I flippin did it again. Typed up 3 paragraphs and then hit tab (to indent) which took my focus off of the typing, and then hit backspace, and lost all my writnig. I need to start typing in a notepad and copying it over here....
In case if you don't want to read this, you don't have to. I know it's long. But I tried to condense my thoughts.
Quizbowl central is a great resource (links have been provided, although it currently is not running).
What I was saying was, if you wish to become a generalist, study quizbowl topics. Like ben said, start with the basics; start with the Fall Novice Tournament or something similar, just to get used to the what quizbowlers refer to as the "canon," or what is commonly asked about. Reading packets is the best way to gain a feel for what commonly is asked about in quizbowl and give syou a good indication for what is good to learn/know about. If you start studying random literature, half of what you study may never come up; that's a waste of time (from a quizbowl perspective; it may be a good book, though :P).
As a starting learner to quizbowl, something that will help you is first, get associated with the pyramid style of questions (starting with obscure stuff, giving the common-knowledge at the end), and once you understand that, write your own questions (of course, write them on things that come up in quizbowl, but don't write the same question you've seen before. If you don't learn something new in writing a question, you wasted your time. Google "writing quizbowl questions" for guides to help you write them). The best way to become good at quizbowl is to LEARN stuff; dont' just read packets, don't just look at lists of facts. Get a feel for what the questions ask, and then do something about it. Study up on your philosophers; write a paper about famous civil war battles. Actually applying your knowledge into writing a paper, giving a lecture, sharing your knowledge, writing questions, etc., will get it to stick in your head, MUCH better than simply staring at a list or rote memorization (granted, memorization does have its perks, but you'll discover those as you get better).
If you're good at science, however, you may wish to specialize just in that. Many good quizbowl teams have one person who specializes in one thing, one in another, and another person for another subject; this allows more in depth knowledge per each subject and is generally more rewarding from the points perspective, at the cost of no one player excelling pointwise (each subject only comes up so many times per round, after all). If your team is already pretty good, you may wish just to specialize, or, if your team is bad or you are a freshman/sophomore (and therefore have much time to improve), start learning as much as you can; which brings me to my next point.
Time. Time is the most important thing you have in practicing quizbowl. If you're not willing to put your own time into it, you'll never be "very good." Seeing as you created an account just to post this a message, I feel like you're willing to improve and put time into it, but my case still stands. Do quizbowl every day; carry around a sheet of quizbowl facts and look at it in your free time during classes. If you can't find the time to do at least a packet a day, you'll never be as good as others, who, I gaurantee, do more than one packet a day.