On the Team Round, the four members of your team can collaborate to solve 10 problems in 20 minutes. Calculators ARE allowed.
Every team has its own "dynamic," so practice together beforehand to figure out strategies that work. Will you collaborate on each problem, or will you "divide and conquer"? Which team member is best at geometry problems? Who has a knack for catching errors? The important thing is this: when the Team Round starts on the day of the competition, you do not want to be staring at each other awkwardly and saying, "Sooo... how do you want to tackle this?"
Personally, I've found that it's useful to first divide up the problems so that each person is responsible for a few. This can be done before the Team Round even starts: "Anna, you get problems 1, 2, and 3. Bob, you get 4, 5, and 6. I'll do problems 7 and 8. Charlie can have 9 and 10." Once the Team Round starts, each person immediately gets to work on his/her own problems; if there are tough roadblocks in solving the problems, or if one person finishes before another, discussion and problem-trading can occur. After all 10 problems have been worked through, the team starts checking the answers. Each team member checks a problem that he/she did not originally work on. Ideally, if there is enough time, each problem will have been solved by at least two different team members who agree on the same answer.
This is just one example of a team strategy. It worked terrifically for us. If it works for your team too, swell. If not, I'm sure you will develop a brilliant attack plan of your own. In any case, the way you will discover these strategies is through PRACTICE. We never decided, "Let's devise a team strategy today!" Instead, it came about naturally, as a pattern after a few practice Team Rounds.
And one more tip: don't talk too loudly! Your opponents are nearby!