One important thing to do before giving up on your new friend is get to know them better. Find out where they are from, what they like to do in their spare time, where they are planning to go to college, and what they want to do with their life. You may find that this sloppy person has some of the same goals as you. Don't judge them before you have had a chance to find out who they really are.
Making a schedule of chores might be a way to settle some differences, and then trade off every week so one person doesn't get stuck washing the dishes every day. This way, all the roommates can pitch in and help keep the living area neat. Some may define neat as being able to eat off the floor. Some may define it as “that lived-in look.” Discuss what neat means to your roommate and see if you can reach a happy medium.
A roommate can also have personal habits that just drive you crazy. They leave the toilet seat up, they place the dishes in the sink instead of the dishwasher, they chew and pop their gum, and they hog the TV or phone all the time. Before you vow to smack your roommate upside the head, have a sit-down and discuss the problems stated above and see what they can do to work on them. But, be prepared. They may have a list of your habits that drive them crazy as well.
Set rules upfront with your roommate about sharing items. You may not want other people in your personal clothes or makeup. You also may not want to lend out your electronics or other items in fear that they may get broken. If your roommate decides to take these items anyway and they do get broken, find a suitable replacement yourself and let them foot the bill. You can also have them replace the item themselves.
Inviting friends over may be an issue, especially if they are showing up at all hours of the night. You need to have a talk and set some rules on when people can come over or call. If you are in college and studying, that ringing telephone or party going on downstairs is very distracting. So set some ground rules before it even gets out of hand.
Learn to be flexible with your roommate. If they screw up one time, let it go and give them another chance to get it right. You may screw up yourself and need another chance. Don't burn your bridges before you have given them a chance to right themselves. If they do something really awful, you have to go with your gut instinct. Only you know how much you can put up with before you blow up, so keep cool and don't let it get to that point.
Have a meeting every couple of weeks to discuss what is going on and how both of you will deal with it. Keeping open the lines of communication may be the thing that saves your roommate and you from driving each other bonkers. This way, you can let each other know what is wrong and how it might be fixed.
Remember, your happiness with your roommate bleeds into your daily life. So choose one that you can get along and live with, and you will have a happy relationship in time. It is the getting to know you part that is always the hardest. So give each other that chance and take it one day at a time.