Cry. Honestly, that's what I do every day, and I live in a one bedroom DC condo with a den, a small walk-in closet, a traditional closet in the den, and a coat closet. Granted, my boyfriend takes the traditional closet and the coat closet, leaving me the small walk-in, but it's not close to enough space. It's so crowded, and I'm very familiar with NYC apartments, so I know mine is like a palace in comparison.
Can you leave out-of-season stuff at your closet in your parents' house, and then swap wardrobes? I have never been good at separating stuff by season, but if you can do that, it would save space.
I also have a long, low shelving unit set up against one wall. This was really good in my last place, where I had a long hallway that wasted a lot of square footage. I put all of my sweaters in there. A sad truth of apartment living is that every piece of furniture you end up purchasing has to have a function. I have a bench that has cabinet space (I put shoes in there), an end table that actually has a pull-out drawer (it's really a nice hamper that is disguised as furniture from Restoration Hardware: http://www.restorationhardware.....rod2440007; I have it in my foyer and put shoes in there), and obviously armoires are always popular (I don't have one). I know that most of this is not going to be feasible for a NYC studio, but maybe one or two would be useful or will give you ideas.
Underbed storage is also an idea. I personally don't do that because I like my bed isolated in case there is ever a bed bug outbreak (I am seriously vigilant about that, most people aren't, but since you're in NYC maybe you are too?), but if you don't mind that, it could be a good option.