How did people learn to fly fpv first. 
Did you use spotter ? Finding it hard alone in a huge field

LOS for the first few minutes (and a lot of walking), then screen. Later I got myself goggles to replace the screen.
At a field, it's easy because you don't have to avoid any obstacles, but it's best to keep yourself moving. Don't try to hover much when beginning, you'll quickly mess it up without much experience thanks to overcorrecting your moves.
Also give your camera at least some tilt (5-10 degrees), so you'll get used to it quicker and get used to being on the move.
Oh and I haven't used a spotter even once. Spotter won't help you to move your sticks. I don't find it that necessary when I'm not flying near other people and the field is mowed so that I can find the quad after crashing it.

Work on your LOS first. It'll get you learning how the sticks affect the quad and lets you build up muscle memory. Also if your fpv system is down you're not completely out of the game.
Check out this post also some very helpful advice:
https://oscarliang.com/learn-fpv-flying-faster/

I'm a member of a flying club so I started just going up and down the runway pulling 180° turns at either end. Getting them tighter and lower. Then added a gate in to get through in the middle. Then try making a course around the 3 runways.

Best advice to take from that if your in a big empty field is to try to pick reference points to aim for. Work on your cornering. Getting it tighter and faster.

A spotter does help (not to mention mandatory for bmfa/saa/fpv uk insurance!) They can help with indicators on your height etc as your going round.

I started with a monitor attached to my radio, but what I found myself doing was "cheating", I would look at the screen but then look up at the quad, which made me feel like I was flying FPV, so I thought I was ready for goggles..WRONG!

First time wearing the goggles I lost all sense of height and found myself at 52,000ft passing a U2 Spy plane, or so it felt, and then I would come back down to earth in a controlled manner..by controlled I mean usually upside down and me banging the sticks left and right up and down trying to get the horizon back..FAIL.

so I went back to basics. found a nice big open area, void of people, buildings and anything else I could possibly hit within 100 metres. Then I laid out some home made Cones on the ground, and put the goggles on and concentrated on flying to the cones and around them and always trying to remember where "Home" was. (side note..first time seeing yourself sitting there with your goggles on while flying your quad is a weird out of body experience).

With practice I was able to fly my course and once happy I pushed myself further out.. I think it very important that you remember any kind of landmark you can so you can navigate your way back..Anything..a certain Tree, Bush, post, tyre tracks on the ground etc.

I wont kid you..FPV flying when starting off is not easy, and yet now, I think nothing of it, and LOS flying is alien to me, even though I flew CP heli's for a while.

Practice is and always will be your best teacher to fpv, not everything you hear, or read may apply to you, we all develop our own way of learning and flying. The key thing we all agree on is , Never give up..It will happen. Honest.

Couple of quick tips from my experience.
- I was trying to learn FPV via monitor for a few months and just could not get the hang of it. Super frustrating and very discouraging at times. Turns out my monitor had pretty poor reception so that definitely did not help.
- Someone suggested using a simulator with my Taranis transmitter. Freerider is a free download and which includes a desert course for free. This helped me learn the basics of taking off and maintaining my height.
- I ended up buying Fatshark googles instead of getting a new monitor. Once I started with the goggles, I very quickly was able to start doing basic skills.

One final tip, when learning try to find an object in the distant and fly towards that. Focus on keeping the quad moving forward.

For me a simulator was a huge help. It got me comfortable with the maneuvers and what to expect out of the quad looking through the FPV camera. I was quite terrible before that. A spotter also helps, for the visual aid and for the words of encouragement.

I recently got my father-in-law flying and between simulator, spotting and using a trainer radio the first day, he was proficient to cruise around on his own the second day.

FPV Freerider and Liftoff were the last few simulators I used, that was months ago, there might be better ones now.

Where are you located? Perhaps we can find you a fly buddy or a local club.

As a beginner still myself (only a few hours tops flying time):
How does one need to act when hitting a branch of a tree? Or any other target, that the quad can get temporarily get stuck on. Is it best to leave the quad to its own on trying to get the previous angle back or should I step in and try to do that for it?
Native instinct is (well, for me anyways) to try and step in, although that usually doesn't help so it'll just crash to ground.
I'm flying with Betaflight.

The times I have been chrashing in tall trees I was lucky enough that one or two props where not stuck. I could just arm it and go all crazy on the sticks and the quad fortunately jumped out of the tree.

I rather meant when it doesn't get stuck per se, but gets tossed around instead.

thank you guys for the extremely helpful advice!

I started flying in LOS after learning on a Hubsan x4. Glad I did. I crashed that thing around my house and yard like I stole it.  I have a small yard with narrow flying paths rimmed by plants and the dreaded kids swing set (prop killer).  I got a ZMR250 kit and built my first "real"quad. After I felt confident with LOS I debated on getting goggles or a monitor. I figured that if I could look up from the screen it would kinda be like a hybrid of LOS/FPV. Plus when I eventually switched to goggles I could use the monitor so my son and wife could watch what I was doing when we went to the parks, and curious bystanders could see what I was doing if they asked, which has happen a few times
with my monitor zip-tied to my controller I slowly began flying it from point A to point B in my yard.  It was really hard but eventually I got able to fly it from one side of my house around to the other side and land it in my hammock.  The hammock became my landing spot of choice.  It felt really cool to be able to pilot it with just the screen around to the other side of the house and then turn it around and fly it back to me.  I got lots of video interference and static when it went around the corner but somehow to me it seemed to make the experience that much cooler, fun, and realistic.  Feeling confidant in my FPV skills I purchased a pair of Quantum V2 goggle kit.  I installed a little FPV camera on the font of the goggles so I could have them on and flip a switch to have a quick last minute check that there were no animals or people wandering close to the Quadcopter. I chose the Quantum because of the price and the fact that I wear pretty thick glasses and the fat sharks don't work with glasses. I did not think the diopters would have been strong enough.  The included video switcher was crap and did not work at all, so using parts I had laying around my workbench I made my own switcher and it works great.
Ok I put the googles on and was like "Crap man" I felt like I was back to square one.  I couldn't control the thing to save my life.  I had no bearing on how high I was flying or what was behind me.  It was like learning all over again.  It was very discouraging. Sometimes I would switch back to LOS just so I could have some fun flying.  My yard was small so it was extra hard to learn it.  I did get to the point where I could zip around the yard and through the swing set without crashing to much.  I was buying lots of props. Ive never really used a spotter and fly alone most of the time.  In a open field it has been easy to get disoriented.  I try to pick a tree to fly back and forth to or sometimes I will just go stand in the field and use my self as the object to fly around or for a landmark.  I've noticed that putting more of an upward tilt on your FPV camera really helps you not look at the ground the whole time.  Sometimes I fly in a field that has three baseball diamonds in a row.  Once I had to land cause of low voltage and I thought I was in the field I took of in.  I took off the goggles thinking I would see the quad near the pitchers mound.  It was there, but it was the third field over. 
Try to pick an object that is very visible to focus on.  Ive had my ZMR for 6 months now and I am pretty comfortable flying around the park and between trees, but I am still learning and have just started to touch thoes PID's.  Ive got much more to learn.
Well  that's my little intro to FPV flying.  Keep trying and it will get easier and its so much fun its addicting.  Intofpv and Oscars blog are the best resource Ive found.

I started on a Hubsan X4 like NimhBot and quickly wanted more. I would suggest the Liftoff Simulator available on steam if you have a transmitter already. I have learned so much from flying on the sim. Its not exactly like real life but it is really helpful to practice FPV.

(06-Sep-2016, 07:08 AM)Mikk36 Wrote: As a beginner still myself (only a few hours tops flying time):
How does one need to act when hitting a branch of a tree? Or any other target, that the quad can get temporarily get stuck on. Is it best to leave the quad to its own on trying to get the previous angle back or should I step in and try to do that for it?
Native instinct is (well, for me anyways) to try and step in, although that usually doesn't help so it'll just crash to ground.
I'm flying with Betaflight.

Each situation is unique. Usually when the quad collides with something, controls are mostly useless. There have been a few times when striking an object alters the flightpath insignificantly enough to recover and resume flying. The general best practice is if control cannot be regained in moments, or if other risk factors - people or property that might collide with the craft, high speed, etc. - disarm the motors. This way at-least you reduce the risk of propeller cuts or further uncontrolled propulsion of the vehicle, tho there is still a 500g+ projectile in flight

Now that I have scared the newbies some, tree and branch impacts and getting stuck is normal and should be expected. Propellers love to get stuck in thin leafy branches. There are two strategies: 

1. Disarm, see if the craft will fall down on it's own. If not - begin retrieval process which includes shaking, pulling, throwing objects. I recently used a tennis ball launcher successfully. I've thrown shoes, plastic water bottles. I've seen friends throw balls, rope with weights attached, just keep in mind what goes up, will come down and be safe.

2. Keep the motors armed if the quad is still falling, or twitch arm to see if it will get loose. You are risking more damage, especially to ESCs and motors due to the high current going through seized motors. I've done it successfully a few times but I have also burned parts. Do at your own risk. Also many flight controllers will not arm unless level, as a safety feature. I generally disable the accelerometer, so that is not an issue, but folks flying level mode should keep in mind. In all cases, be ready to disarm and dodge falling objects and make sure you and others are safe.

People and other property haven't become an issue yet thanks to selecting the flying area where I don't cross paths with other people or their property (flying around in a public park/forested area, essentially it's just a large field where the lawn gets mowed occasionally).
But yeah, the question was about getting hit from twigs and having the last course changed (which usually includes spinning as an extra).
Will try to keep the fingers off the sticks then until it becomes stable again next time when it happens.