How do you hack into someone's account?
Firstly, it is always easier to hack someone's account if you know him/her. Since there is already some trust between the two, be it BF, GF or just a friend it gets easier.
The easiest way is to copy the html code of say gmail/facebox or simply even a screen shot, host it on your server and send you a link saying "check this new feature on Gmail/Facebook". If it is an email from a friend, ofcourse you are going to check it. If you trust that person and yo blindly click on the link and enter your credentials, the script will send your email and pwd to him/her. Always before clicking on any link see what the URL reads, if for example it says "http://blahblah/gmail" or "http://gmailpak.com" do not open it!
The second way is if the two of you share a computer. There are dozens of programs available to download or some one could easily code a program that is called a "Key Logger". A key logger basically records every key pressed on the key board and is capable of emailing the logs to somebody. It will not show up unless a specific combination of keys is pressed.
lastly, somebody knows you so well that its easy for them to crack your password by simply guessing it or he/she has seen you type the letters and thus know your password.
Your password is your responsibility, keep your password strong and stay smart! your avg joe cannot write a script that can hack your account magically, chances are you helped him in some way.
Stay Smart People!