Deciding what you absolutely cannot live without and what can stay at home is often an agonizing process. Use logic when packing. Do your research on the climate of your study abroad destination. If you're going to be at your study abroad destination during summer months, for example, leave the heavy winter coat at home. In addition to climate, think about events you'll be attending, and so on. Also, pay attention to your host university or study abroad program's suggestions on packing. They're the experts on your host country's climate and culture and the things you need to live there.
Some other variables to keep in mind when packing are
When are you going to get to your final location?
Are you getting off the plane and going right to your new home to settle in?
Does your program have a tour or orientation program planned so that it may be a few days before you arrive at your final destination?

Pack everything you need for those first few days at the top of your suitcase so you have easy access to it. If your program is a study tour, and you won't be settling anywhere for any considerable length of time, you'll constantly be carrying whatever you brought, so limit yourself to a moderate-sized bag and a small carry-on bag in which you can keep valuables and critical travel documents (passports, airline tickets, and so on.).

Ask other students who have already studied abroad with your program for their advice about what you need to take and what you can leave at home.
Wondering about wardrobe

Clothing takes up the most space in your suitcase when you pack to go abroad, and you want to choose it carefully. Remember that safety abroad begins with what you pack. You want to dress conservatively to avoid drawing attention to yourself, and try to look as unlike a tourist or an American as possible. Don't wear tennis shoes or sneakers (In other countries, sneakers are much different than what we wear in the U.S.). Baseball hats are a dead giveaway that you're an American, as are sweatpants. Wearing black is usually safe. Also, wear skirts that are of a conservative length (knee length). In other words, aim to blend in, and avoid wearing expensive-looking jewelry or clothing. Note: Clothing that is too casual for where you're studying can signal that you're a tourist.

Here's a list of things to remember when packing clothing for your trip abroad:
Clothes need to compliment each other so you can easily mix and match them for a wide variety of outfits. Dark (black, navy, purple, green) or neutral (all browns and shades of gray) colored clothing is not only easy to interchange, but also tends to hide any dirt or stains you inevitably acquire along the way.
Try packing clothes made of fabrics that require little care. Wrinkle-free and cotton-knit blend clothes are most convenient and are extremely easy to pack, thus creating more space in your suitcase because you can tightly roll items that won't wrinkle. I also recommend rayon/polyester/spandex blend clothes for traveling. They are good for multiple seasons, take up little room in luggage, are almost impossible to wrinkle, and dry relatively quickly after being washed.
Avoid packing anything that requires dry cleaning because it's too much of a hassle. Put dresses, suits, and shirts in plastic bags (dry-cleaning bags) to cut down on wrinkling. If your suitcase has a garment cover designed to accommodate hanging items, use it.
Waterproof clothing is a great idea, particularly when you're headed for a rainy climate or any region where you'll be studying during the wet season. At the very least, bring a raincoat and a pair of waterproof shoes. A travel raincoat takes up little space and is easily rolled up so you can even carry it around in your school bag. You'll be more comfortable and less likely to overheat if you have a raincoat made of a breathable fabric.
If you're traveling to a cooler climate, be aware that dressing in layers is key! Layering clothes is more effective than hauling around bulky sweaters or coats.
Pack a change of clothes in your carry-on luggage just in case your luggage gets lost during your travels.
If you know that you will not be able to use a clothes dryer at your study abroad destination, remember that jeans and bulky clothes take forever to dry.
Pack heavier items, like shoes, at the bottom of a suitcase. Wear the pair of shoes that would take up the most space in a suitcase while you're on the plane. Put your shoes in shoe bags (or thoroughly clean the soles) before packing them so your clothes don't get dirty. Stuff small items such as socks or travel-size toiletries inside your shoes to save space.
Consider packing your clothes in plastic bags sorted by type of garment (In other words, have different bags for shirts, pants, undergarments, and so on). This enables you to easily find what you're looking for without taking everything out of your bag and then having to repack.