The cool kids use valve core removers, super cool kids (not naming names) use the kind that are your valve caps so you always have them. They are available at checkers and maybe autozone.
As for tire PSI that really depends alot on the vehicle. Weight, tire size, tire weight rating, etc... will all play into it. For example on my old jeep on the road i ran my tires at 35 psi. It had 32s. On my current jeep i run the 37s at 22 psi on highway. For offroading starting at 15 is probably a good idea. If you feel you need more traction then go down in psi. The only trouble is if you go too low you can pop a bead. I used to run 8psi on my old jeep and never had an issue, i currently run 12 psi. Trial and error is the easiest method but there is actually a science behind it. One of the magazines i read had a whole article on it that was pretty enlightening but i wont bore you with details.
Simply put just start at 15 psi and go from there.
It was a Jeep thing, but all that stuff broke
92 Jeep YJ Wrangler
"YJ's are for poor people" - Brian