rules at home

[my3girls272]

My 18yr old chose to live at home and go to a local university. I'm lovin' having her at home.  Problem is....she comes and goes as she pleases.  I have always been the type to keep my thumb on her and check up on her and it feels good to give her some freedom. However, I guess I don't know what rules are appropriate. She is taking 15 hrs (2 night classes) and works about 20+ hrs per week.  By the time she throws in her social life, she is rarely home.  She has a group of friends who an apartment so she spends a lot of time at their place...probably spends the night with them 2-3 nights/week.  She also has a boyfriend.  She leaves her room a mess and it seems that I have to tell her 5 times to put a plate in the sink!!!  She is usually very disciplined with school and makes good grades.  However, with all she is trying to juggle I'm not sure how she's doing and no grades have been posted yet.  Any suggestions on rules of the house for this age???