as whippy said, its not a big deal.
just put a ratchet on the bolt on the front of the crank shaft, make sure its on tighten, put the car in neutral, and start turning the engine over (key out of the ingnition to ensure you dont start it or something. LOL)
You can place something "soft" (IE: a pencil, a chop-stick, a broken paint stick, etc. ect) in the spark plug hole to watch the piston go up and down.
Ensure you go through the intake and the exhaust stroke (this means you have to watch the piston go up and down a minimum of 4 times [5 times to be safe] in order to ensure it did the entire cycle of the engine.)
if a valve hits a piston, you wont be able to continue turning it over. you just saved your engine for a death sentence.
for future reference, engine builders put a glop of clay in their engine during the assembly process so the valves leave an indentation in the clay to ensure that their pistons' customized dimples and valves are mating up properly. They turn the engine over by hand, remove the heads, inspect the clay, correct as needed. once the clay shows them the signs they are looking for, they remove it before final assembly.