1) Read up on how to root before you start
You would think this would be obvious would't you? But none just knows how to root their brand new Galaxy S2. There is no Neo, this isn't the Matrix where you can just do it because you are the one. We all ready somewhere how to get root access to our phones and there is no shame in getting your information from a trustworthy source. Also make sure you read the entire how-to when you find it because missing a step could mean you'll be using that Galaxy Tab of yours as a paper weight instead of checking whats going on in the forums. This also inculdes asking for help if you need it. Remember there is no shame is asking when you don't know.
2) Research YOUR phone
Rooting is a phone-specific so how you root, lets say, an HTC Desire is not how you root my beloved Galaxy S2. So remember to find information on your exact phone including carrier and seral number!
3) Learn how to hit the do-over button
There are certian times you don't want your phone rooted (Say if you ever want to take it back to the store from one reason or another) so learn how to de-root your phone. This is also a good thing to know incase you screw it up the first time and need to de-bick-ify your hand set.
4) Charge that bad boy up
Do you know what brain surgery is? Yeah, I thought so. Now imagine you're sitting on the operating table with some guys hands wrist deep in your frontal lob when all of a sudden the lights go out. Not a pretty picture is it? Its the same thing with your phone. Rooting is like brain surgery for your Android so go a head and make sure your battery is fully charged. If not you risk labotomizing the poor guy.
Hmmm thats about it for now if anything else occurs to me Ill add it later. Happy rooting!