I bought Nair bikini wax strips...and this is the first time I'm waxing...help!?!?

You can wax off as much hair as you like. Personally, I prefer to wax off most of the hair down the hair and I shave off whatever's left. You should trim if it's more than 1/2 an inch. Bikini waxing in general is painful, but it depends on your pain tolerance. To reduce the pain, I waxed off small amounts of hair at a time. I would say that the pain is like ripping off a large band-aid. The pain is bearable. I don't think the area would still be red by tomorrow. Good luck!