Don't nag. This is a hard one, especially for those who are not artists. But being an artist myself, I still find myself nagging my husband. There are better ways of asking for something to be done or reminding him about something. Asking in a nice way is key. If they forget, instead of nagging in an angry way, try to convey the way that it hurt you. After all, anger is a byproduct of being hurt.
Watch for depression. It's a wonderful thing that whoever you are with is lucky enough to have you in their lives. Artists can become very alone in their creative depression bouts, and that is a dangerous thing. Make sure that they do have their necessary alone time because that is also necessary, and will make your life a lot easier. But also remind them that you are there for them. Be a shoulder to cry on if they need it.
Be careful when you are arguing about money troubles. Try to figure out how to work through it together instead of placing all of the burden on them. Being an artist isn't easy. At times, my husband and I both wish we could be satisfied with regular jobs that bring in regular cash. However, we wouldn't trade in being artists for anything in the end.
Give them their space. This doesn't mean that they don't love you or are tired of you. Artists need their space to breathe for their own creativity. Give them what I like to call "alone time."
In general, artists tend to be a bit messy! My husband is a tornado and I am not much better naturally. I've had to learn to be more organized, otherwise the house would be more of a wreck than it is! For one, you cannot expect the house to be spotless all the time. Artists will have books, papers, supplies, and everything else, everywhere! This will be extremely hard for people who are used to having everything in its place. If possible, have a specific room for creating art, or at least a good sized area in the house. This area either needs to contain or be close to books and the computer. Also think of things in big sections. These sections will be easier for the artist to separate things (i.e. hamper for dirty laundry, basket in the front for mail and other papers that need to be looked at). Artists can see the big picture, and once that is maintained, will pay attention to the details. Also, categorizing things where you can visually see them will help keep things organized.