Communication is
biggest key to any relationship, and roommates are no different.Open up channels of communication early: Talk frankly about how excited you are, if you are nervous, etc. Get it out; they probably feel same way. Doing so will establish that you're both committed to making it work, even when honeymoon is over.
Look at yourself and your own habits, think of what a roommate would most likely complain about and point blank say "Look, if my [snoring, late nights, music, etc] become a problem tell me". In selecting a roommate you want to make sure that your lifestyles won't conflict.
Message Board
Setup a flat message board, such as a fridge whiteboard or notepad in kitchen area. Some things, though, are better to talk about in person. Don't say, "Clean bathroom"; say "Give me a call when you get a chance". Nobody likes to be told what to do or be "talked at", think about things from their shoes, even if you may be mad at them.
Speaking of getting mad ... avoid waiting until your roommate steps on your toes before saying something. When you sense a situation could occur talk to them ahead of time. Don't stew about things, get it out, chances are he/she will appreciate you talking to them instead of moping around. A little effort and maturity is a worthwhile investment, it will go a long way towards helping you enjoy your place. Sometimes you will have to be bigger man, so to say
Disagreements
Handling disagreements in a functional way is difficult. Like any relationship, it will have its ups and downs. How things go when it's "down" determines how happy you are.
Remember, you're unhappy (to put it mildly), and your goal is to become happy again. This will involve some charm and charisma on your part. Being one to initiate things is usually best way to accomplish this: It puts you in control, demonstrates your willingness to work things out, and takes burden off of them somewhat.
Think through a given situation before you approach your roommate, run through conversation in your head. What are you going to say? What are they going to say back? And so forth.
Remember, it will take both of you to make things work, part of that requires you to understand your roommate's position. The other is to effectively communicate yours, and persuade them into seeing it. Unless you're living with a complete jerk, your roommate will be willing to work with you once he understands where you are coming from. Using understanding of his position to illuminate yours will let you talk as non-combatively as possible.
Some things cannot be lined with roses, though. If you have to be blunt, say so. Add that you're not trying to be unreasonable, but you feel strongly, and want to work things out.
Nothing is gained if you "suck it up" or by backing down when its time to talk. The same can be said of going on a rant and yelling at them. The key is to get your point across without putting them on defensive. Once someone is in a defensive mood any rational conversation is impossible. Table a discussion for an hour if things get heated up, but don't let them drag out over days. That's days of unresolved misery for you.
Avoid heat of passion "discussions" by bringing up problems before they come to a boiling point. Again, talk to your roommate. Telling your friends for weeks about how they have been annoying you will eventually culminate with you loosing your cool. The longer you put off talking to other person longer you're unhappy.
