Making the most of quiz bowl practice
The first tournaments of the year are quickly approaching, and you might be starting to practice for tournaments with your team. Since you have limited time to meet with your team for practice, how do you optimize your time at practice?
Read Questions in Practice
The best way to prepare students to answer questions in tournaments is to have them answer questions in practice. Read sample questions in practice and have them answer them. (If you have access to buzzers, let them buzz in to answer the questions. Otherwise, they can slap the table or yell out "buzz" or indicate a buzz in some other manner.)
There are two primary sources to get practice questions. You can buy old questions from NAQT to use for practice. (When you go to a tournament run on NAQT questions, you should get a copy of them that you can use for future practice.) NAQT does not release their questions to public domain, but many other question writers do at the end of the year. You can find an archive of these questions on the quiz bowl packet archive to freely download.
With new players, you may want to start with novice questions. (These are the A series on the NAQT order form, or any high school tournament marked with a  on the archive.) As players gain more experience, you should increase the difficulty of the questions you read. As long as your players don't get frustrated or demoralized by hard questions, it's a good idea to read questions that are slightly harder than the tournaments you play. The easy clues in these questions will still show up as middle or hard clues in easier tournaments, and players learn more.
Encourage players to take notes on the questions--in practice, as well as in tournaments. They don't need to write down everything, but they should take notes on things that they are likely to look up and study later on. I recommend that they make note of things that 1) sound really interesting; or 2) is something they know, and they think they should have been able to buzz in earlier; or 3) something that keeps coming up and nobody on the team answers. Outside of practice, students can read more about these things, learn more clues, and be able buzz in earlier in the future.
Speed Check questions
In addition to the pyramidal questions used in tournaments, you may want to occasionally read speed check questions. (You can order these from NAQT, or create your own by taking the giveaway questions in a tournament and editing them to be a complete question.) This is a good way to warm up for practice, and gives students exposure to a lot of giveaway clues in a short time. This won't help students buzz in early, but it will help them get questions at the giveaway, which may be useful for topics that they struggle with, like art or music.
What to do with a variety of skill levels
If you are fortunate enough to have a large team with players at a variety of skill levels--new players, experienced players, and players in between--it may be hard to have an effective practice that meets the needs of all your players.
If you have the luxury of an assistant coach or parent volunteer, you can have them read to the varsity team while you are with the JV team, and vice versa. If not, a lot of times experienced players are happy to read questions to each other.
There are a variety of things you can do in practice to help inexperienced players. You can give them multiple buzzes to encourage them to buzz early with guesses. You can stop reading after clues and poll them for possible answers. (Ask: What is this question asking for? What might be some possible answers that satisfy these clues? For those answers, what are some other clues you might expect to hear?)
If you cannot separate new players from experienced players, there are some things you can do with a mixed group. You can give novice players multiple buzzes. You can restrict experienced players from buzzing by having them only buzz during the first sentence or at the end of the question. You might also pair up an experienced player with a novice player and have the experienced player buzz in when he or she thinks that the novice player knows the answer (or should know the answer), and have the novice player answer.
When possible, practice under game conditions. Split up the team into two teams that are as even strength as you can manage, and have them play each other. Use buzzers, enforce timing rules and observe the guidelines for acceptable answers. (And be strict about it!) Keep score and declare a winner and top individual scores. This not only gives the players a feel for the game, but it also helps you see how the students react to more formal games. Keeping score lets you track which players or combination of players do well.
It's important for students to learn topics on their own. You may want to have students make short presentations to the whole team about some topic that comes up in quiz bowl and the team struggles with. (Keep it short, or the presentations can eat up too much time. The topics should be pretty narrowly focused.)
You might invite other teachers to practice to give short lectures on certain topics. In addition to teaching your players about some topics, it gives ownership of the team to other teachers, and might lead to greater visibility for the team, and the teachers might start recommending students to play quiz bowl.
Read student-written questions
For experienced players, writing questions is a great way to learn about topics. Not only do they learn about the topic when writing, but it gives insight to what clues are good, and lets players anticipate where the question is going. You might ask experienced players to write a handful of questions a week, and then read them in practice to get feedback on the question.
Don't forget to keep practice fun and engage the students. The more they enjoy practice, the more they'll come back. Don't be afraid to switch things up when practices are getting stale and students are getting restless. You may occasionally want to bring rewards, read pop culture packets, or play other games like Trivial Pursuit just to give students an occasional break.