I finished painting and wet sanding. I'm a total rookie so I need to know what to look for in a buffer, air vs. electric? and anything else I'll need. I used single stage urethane paint, and the color is orange. I don't know if that makes a difference.

Well....what works for me:
Wet sand with 1500A paper to remove dust, etc.
Makita (9227C) variable speed electric polisher using Norton Liquid Ice polish (97116) with a coarse foam pad.
Slow down speed and finish with a soft foam finishing pad.
All these items are available at KMS Tools, if you're near there.

Your Orange single stage will buff out nicely.

For best results IMO, use a waffle foam 3M pad, 3M heavy cut/or Meguires, then go over it with a med cut or just hit it with some glaze..I prefer the dewalt buffers, turn it all the way DOWN! to avoid swirling as much as possible. Be carefull with the pad on edges it will burn through a lot if your not careful.

I knew this was "next" and there are as many "opinions" on buffing as paintinig.;)
The dimple or waffle style pads are the "safe" way to go. They cut well and generally keep you from burning thru. I prefer wool twisted and 3M Perfectit Regular Cut II but I go 1200 and buff from there.:lol:
I have a shop FULL of different pads and compounds for DIFFERENT jobs and it just depends on "what" I want and how far I'm willing to go to get there. I do custom work and it demands a variety of stuff to get there.
In YOUR case,I'd chose a 3M White waffle compound pad and whatever initial cut compound you can get local.Perfectit II Regular Cut or III Extra cut with a 1500 sand and then a Black waffle pad with Swirl Remover.
Buffer is whatever you can afford. I use a Harbor VARIABLE speed model with a MAX RPM of 3000. Usually run around 1200 and as i step up in finish,step up the RPM to nothing above 2000,usually 1500 or a little more.
Buffing is like sex, Start SLOW and finish HARD.
Work a 1' square area at a time as you go. Trying to go whole hog and work the whole panel is bad news. Just work an area at a time and blend them together.You'll LEARN and come back and ask questions.
Be SURE to WASH between compounds. Once you finish with ONE,CLEAN the panel and switch pads and go again. If you leave the previous compound ON the panel,and you WILL,your grinding with the SAME stuff,so CLEAN it or you'll end up with cutting compound in your finishing pad.OUCH!!

I agree with Mike here. The keys here, just to reitterate, are...1)clean pads and panels 2)work small areas at a time. Those are key to your sucess coming easier to you.

I personally use a Makita buffer myself, I like the ballance and the way it fits my hands best. That is all up to what you like and what is available to you. I also use the 3m and/or Maguires compounds depending on the job.

mike and dd have given you great advice clean panels and work a small area at at a time and you should have great results.
the one thing about paint and body work is PATIENCE.

Go on you tube. there are a ton of how-to videos that go step by step on buffing and polishing. they really help.

About the only other thing I do is depending on how many coats of clear is, wetsand with 1000 to remove the rough stuff then 1200 or 1500 to cut those 1000 grit scratches then 2000 to cut those. The finer you sand the less work it is to buff. As far as the different compounds go I'm kinda anal about it, I wash the whole vehicle with soap and water between them to keep and residue left from the cutting compound. All it takes is for you to be using your swirl mark remover and get a pinch of the other in it to ruin your day [ or to just cuss out yourself for not washing] ;-)

i dont use the trizact or 3m system but this gives you a great idea of what is involved in the process. i use meguirs
http://shows.implex.tv/3MTV/Root/AAD/4196/player_6816.htm?d=1245032441562