I want to learn to do a standing backflip so that I can feel comfortable moving on to higher backflips and wallflips, then eventually to frontflips and sideflips and twistflips and what have you.

So, I've heard that these are slightly easier than frontflips, and I've looked at a bunch of the tutorial videos and readings, but I still don't feel comfortable trying one, even on grass. It seems like they list nothing to do to prepare yourself first - they just tell you what to do when you do it. Is it possible to sustain very serious injury (like, broken bones and neck) from an improper backflip (not tucking enough, over-rotating, under-rotating, not enough jump height, and whatnot), or am I just scaring myself out of trying? And what does it mean to have a friend 'spot' you? Should I bring a bed matress outside and try it out on that?

My friend and I have been thinking of taking gymnastics as a preparation for doing flips, learning balance, and building muscle. Is this a good idea in your experiance?

Thanks for any feedback!

yea go to open gym and it wiill be easy thats how i learned ..or have a friend spot you ,and then theirs a last choice and thats just go for it and its not scary once you get over it 

It sounds like you already know what to do.
There is going to be a part that is simply getting over the fear and just doing it with full commitment.
Do not forget to jump.  Jump THEN flip, not jump AND flip.  There is a difference.

It might be a good idea to make sure you are comfortable with going backwards first (eg. use a trampoline).  You'll be using the wrong movement/technique on a trampoline as you would on the ground, but it would help you get over the fear.  Just remember you are using a different movement on the trampoline than you are on the ground and it isn't the same.

obviously, do it on grass or pads first.  I don't think you'd be stupid enough to try it on a hard surface, like concrete or something.
and make sure you have a good spotter who knows what to do.  also, make sure your spotter can spot you (ie. weighs more than you and is physically capable or properly spotting you).

I'd also recommend learning on flat ground before doing a ton of them from height.  otherwise you might have some trouble learning to jump properly.

Today I really got my friend into free running and I was hoping he could spot me.  He is probably a few ponds lighter than me.  Should he still be able to spot me alright?

Well I did my first backflip in gym mats a couple of months ago and I didn't do the flip fast enough which got me landing with my ankle. I think the problem with starting flips is the fear. For the moment you are in the air you are not used to your body being in any other position other than standing.

What I will do to get flips going is practice them in a pool so I can get used to the turns I need to do.