Strongly recommend does not do this post justice. If you do not already use Google's 2-step verification - click on this link and either follow the directions on the site - or watch the short 1 minute 16 second video embedded below.
The 2-step verification will even protect your account when someone tries to enter your correct credentials but on a device that you have not used before. So, if you try to get into your Google account from a device that you have not used in the past, be sure to have your phone handy for the 6 digit security code they send you. You can then decide to either add that device to your "trusted devices" or not.
There are many sites that offer 2-step verification (Facebook, Yahoo!, Dropbox). Always good to be on the safe side!
As always, any questions let me know!