Another cool and EASY idea (since it's the first of the year still - I mean technically speaking and all!) go IMPLIMENT IT NOW! This was rather easy for me since I just finished a load of laundry and had to put it away anyway. Turn all your hangers around - as you put them back in the closet they will go back in the right way and you'll KNOW for certain which clothes you are wearing and what you aren't when you check back in June and take out all seasonal clothes that weren't worn. and DUH you'll know which ones weren't worn because the hangers are still back wards!
Now I know that it will be a little hard because some things have sentimental value or you didn't get to wear it because it was a summer tank top and in your area it doesn't get worn till June or July (not the case in Texas I have a feeing I'll be wearing my summeriest of tank tops in MARCH!)