I'm in the middle of my timing belt taking a break and there is one thing that gets me every time.
Just a tip, the timing marks will line up perfectly. If you run into the crank and oil pump marks being just barely off target, try this tip. As quoted from luv2rallye's tech guide:
NOTE: THE EXHAUST CAMSHAFT SPROCKET MAY ROTATE IN THE COUNTERCLOCKWISE DIRECTION AS THE BELT IS TENSIONED. THIS SHOULD BE CONSIDERED WHEN INSTALLING THE TIMING BELT. If the camshaft sprocket timing marks don't line up after tensioning the belt with all the other timing marks lined up, loosen the belt and retension it, but try rotating the exhaust sprocket slightly clockwise (1 tooth off)
(Timing belt tensioning tips (for 4g63 turbo)