When adjusting my valves, I just turn the engine by hand, using a ratchet wrench with a allen bit on it, in the alternator bolt (remember to disconnect your battery before removing the front cover) until one piston is at TDC - using my drift from my tool kit, I feel when the piston is at the top.
On one side of the engine, you are at compression, with both valves closed. This is the side you want to adjust, first. Both rockers SHOULD have some free play on this side.
The other side should have the exhaust valve open (I think).
After you finish with the first side, move to the other side, put the drift in the sparkplug hole, and again, rotate the engine until the piston drops and comes back. You should now be on compression for the 2nd side.
You can also use a plastic straw for a drift - that way there is nothing hard in there. Someone once mentioned using a screwdriver, but it is possible to break something off in there. The drift in the tool kit is nice and solid with a round head. Go slow and you should have no problems. The piston does move quickly in there!
A lot of folks use the rear tire with the transmission in 2nd gear to turn the engine. I could never get comfortable with that.