The only way to be 100% hack proof is to not put anything online and unplug the cable. I know, that's not reasonable.
Your best bet is using two factor authentication for any website or service which offers it. Twitter recently enabled it and google has it for some time. Facebook has a version of it.
Here's some stuff to read to get you started:
Two factor authentication News, Videos, Reviews and Gossip - Lifehacker
Facebook Login Approvals:
https://www.facebook.com/notes/facebook-engineering/introducing-login-approvals/10150172618258920
Also, don't ever use the same passwords at multiple websites. If you can't remember 100 different passwords (who can?), then use a password manager like LastPass. They have plugins for the most popular browsers and can log into websites for you. LastPass also has two factor authentication to their service. Good luck.