Hmmm...well to be honest the first thing that comes to mind when someone says "personal habits" is cleanliness and hygiene!
I'm sure that's not what they mean though. I'm guessing it means the basics about your lifestyle that may or may not be compatible with someone else. Maybe things like:
Introvert or extrovert - liking to go out/party vs. being a homebody
Detail-oriented vs. big picture person
Exercise, diet, fitness, health
Pets and how important they are to you
Hope that helps.