Unlike this poor boy who looks like he's having to do ancient Chinese or Hebrew, your homework won't be as difficult, but it is is as important.
When it comes to sending your work out, it is important to understand their needs. Publishing houses' needs are quite different from magazines. And educational houses needs are different from trade houses. And so on. Research several places to see where you want to send your work. Then, go to their website, see what their requirements are. What do they want - one page summary? The first two chapters? A chapter and a summary? Does the house say it wants modern fantasy and you've written a historical novel? Then move on and find the house that loves historical novels. Is your historical novel about 16th century France a little too close to a house's historical novel about 16th century France? Then perhaps that's not the perfect fit either. Move on and see who is looking for historical novels, but has nothing about 16th century France. Nothing will make a greater impact than following their instructions.
Want to get a little extra credit? Do a little more research and find out what books or stories the particular editor may have worked on, or profuses to love. It may not necessarily get you published, but it may lead to a hand-written note from the editor instead of a form rejection, and may make the editor more open to accepting more of your work.