There are plenty of problems to worry about when you move in with someone. One thing that tends to get overlooked are the little, everyday habits we have that seem normal, but may gross out others.
Some habits may be perfectly fine if you're living alone but become gross when you're in close proximity with others. For example, putting pizza crusts back in the pizza box before grabbing another slice doesn't matter if you're the only one eating, but it gets icky if you have to share that pie (sorry roomies!). As Apartment Therapy puts it:
The most entertaining way to broach the topic would be a viewing of the Sex & The City episode in which Charlotte deals with Harry's tea bag habits ("A Woman's Right To Shoes", Season 6 Episode 9), but the best way is probably just to be aware of your own actions and ask about things as they come up. If you're drinking the previous day's coffee, cutting your nails, rinsing a dish you need rather than properly washing it, or enjoying a nice floor picnic, you can casually ask, "Is this gross? Or not gross?"
Of course, many habits are just differences in personality that will take some getting used to (you shower in the morning, your partner or roommate showers in the evening). However, spending a week or so examining your daily habits both before and after you move in can help prevent conflicts before they arise.
Home Habits: The Gross-o-Meter [Apartment Therapy]