In general, it is a bad idea to re-use passwords among web sites. If there is a security breach at one site, or you use your password at a site which doesn't take proper precautions in the first place, your password could be compromised.

One easy way to do this is to come up with a "base" password that you then modify based on the name of the site on which it is being used. Your base password should be secure (i.e., uses a number, a lower-case letter, and an upper-case letter) to start. You can then use any of these techniques, or come up with one of your own, to modify the password based on the name of the site.

For these example, assume that the base password is "Mon1ca" and the site on which it is being used is "tipstrs":

1 - Take the first two letters of the site name and prepend them to the base password, take the last two letters of the site name and append them to the base password: tiMon1cars

2 - Take the same site letters as in case (1), but put the ending letters at the front, and the starting letter at the back: rsMon1cati

3 - Take the same site letters as in case (1) but swap the letters before you use them: itMon1casr

4 - Take the same site letters as in case (1), but swap the letters and the position, as in (2): srMon1cait

You can see them patterns here that are available. You can also try using three letters from the site name with similar iterations. In either case, you come up with passwords that are secure, secure across sites, and easy to remember.