The first and the most important thing is that you should understand that git is different. For example it uses staging area (so called index) for iteratively preparing commits. This and other great and unique features of git make it really superrior to hg and other SCMs i've ever seen, so go read its documentaion - you would not regret!
... proselytize to those who have not switched to a distrubuted VCS yet, but trying to convert a git user to Mercurial (or vice-versa) is a waste of everyone's time and energy. If you want to...