What happens if someone was able to access your facebook account?

[MISSME]

I was out of town for a week and during this time did not have an access to a computer. When I got home and checked my Facebook, Facebook notified me that my account was access from an area close to Dallas,TX. I live in the MidWest. I had to change my password. But how was this person able to do this? What steps should I take next to avoid this happening again in the future?

[jason-q]

Change password often and use strange combinations of numbers letters.