kleinbl00's advice is good.

a few further bits of advice:

1.) Trust yourself, and expect yourself to be responsible.

The first thing you will notice is that no one (to an extent) will be there to be a safety net for all the small things in your life. You mention Bills, etc. For me, the paying of the bills is not necessarily the problem (though sometimes working and making money does get in the way of things i want/need to do), it is the motions of paying them - taking the time to actually DO it, that's the rub.

Side note: pay your bills on time. Banks don't like when you're tardy.

2.) If you're a schedule maker, or even if you're not, make time in your life to catch up on the things that need doing: Laundry, vacuuming, cleaning the bathroom.

3.) COMMUNICATE: "House Rules" are a little silly, but having some basic points to anchor your relationship with your room mate is a good idea. People differ, so it's more of a matter of metering out your differences than setting "rules" proper. If you're a morning person and love listening to music while you cook, your night owl room mate might appreciate you wearing headphones as you dance in your socks.

as always, "your mileage may vary", and others will as well.