My current mission requires me to arrest 5 criminals. But I have practically no crime.
How can I increase the crime rate?
First of all, fire all cops and keep any police stations closed. Working police stations actively reduce the crime rate.
Second, make sure you have way more citizens than housing or jobs. Shacks increase crime rate, and only long-term unemployed people actually become criminals.
Third, if you have a Bar, issue the Mardi Gras Festival edict -- it increases both tourism and crime rate.
EDIT: I think there are a few more edicts that can affect the crime rate; I'll see about expanding this a bit when I get home tonight and sit down behind a computer that can play the game.
EDIT 2 Okay, if you have Modern Times, also make sure you have the Police State edict deactivated (obvious reasons), and enable Prohibition. Note that the latter will seriously annoy non-Religious tropicans because you just closed every pub and nightclub by banning alcohol, so not getting revolts becomes a nontrivial exercise...