intake vacuum leak help

I was retorqueing my intake and when I started to tighten the bolt next to the drivers side center my rpm's jumped from 750 to almost 1800 just from tightening the bolts. I know this means I was sucking some air most likely. What is the best and most safe way to check the manifold for vacuum leaks? I've used several methods before but thought I would ask you guys to see what unfolds.