R30 and R34 have it right - divide the space into rooms, probably at least four (bedroom, living room, kitchen, and office), using area rugs, bookcases, paint, furniture arrangement. You will want the separation of space so you can "get away from yourself" especially if you're working from home, so your bed doesn't become your desk. The store has to be "closed" sometime.
Also correct: do your discarding before you move. You'll probably do another purge once you move in, but the bigger purge should be before you go.
With regard to furniture, it's all about scale and portability, that you don't buy things too large for the room. Measure what you have space for, then shop. That means a loveseat that doesn't have huge arms instead of a sofa, and a sleeper loveseat to turn the "living room" into the "guest room" if you're having company from out of town. Nice folding chairs (if your building doesn't supply) are a good investment if you're having people over frequently.
Your kitchen table should be drop-leaf, if you like to have company, so it can open up to seat four or six but folds down to seat two when it's just you at home.
I would agree with the Murphy bed suggestion if you know you're going to stay in the apartment any significant length of time, or if you're going to entertain at the apartment and need the floorspace.
Finally, regarding storage, there's one direction to go, and that's UP. If you have a lot of stuff and can't downsize, think floor-to-ceiling bookcases. Your desk should have a hutch on top. Keep things off the floor so you can clean, find things that are tall with a smaller footprint. You never want to have so much stuff that you have to move things out of the way to get the thing you want. You also don't want so much stacked in the bookcases that it feels like there's shelving everywhere and you live in a warehouse and one good earthquake would do you in.
Remember the value of negative space. You want closets, shelves, etc. at least 25% empty when you complete the move so you don't feel crammed to the max from day one.
Mirrors and light will make the space look bigger, as will light color fabrics and paint. If you want to use a darker color, use a supersaturated one. Wall mount the TV. Even the ottoman and (small) coffee table can be used for storage.