These can vary quite a bit...I've played quite a few tourneys, and the games vary. Often the pay tables are different from what you would normally see.
Not all of them are timed, but most are, so it usually pays to get in as many hands as possible. Some have "pool" of credits that you must use or lose, and I always want to get in every possible play!
The math gurus may be able to give you better play strategy, but I always go for the best payoff in the short term.....not necessarily the best long term strategy. For instance, I might hold A-10 suited, or hold a pair of face cards and drop a second pair, etc.
Ultimately, you might not see the game details with enough advance time to really prepare much. I always avoid the early rounds, so that I can watch others and get a few minutes to study the pay table, as well as the machine's mechanical functioning.
No doubt there are better experts than me in this group, so perhaps one of them has advice that is more mathematically sound. Good luck!