I've usually done Tabata with four exercises at a time, for instance pullups, pushups, situps, squats. There's no rest between movements, and your "score" is the lowest number of reps you did in one set. So it becomes a 16 minute workout that looks for sustained work. I find that it's an interesting approach that seems to work very well, and over time my numbers have changed little by little.

For instance, I know I can do 13 squats per round for 8 rounds, but next workout I'll try for 14. The "trick" is that if I only end up doing 12, say in the last round because I'm tired, then my score for squats is actually lower (12).