There have been tips for this posted before, generally not in this topic which is for bugs & crashes. Usually over in the main topic or the Strategy & Tips subtopic.
Here are 3 tips.
1) Use maps of a reasonable size. The bigger the map, the slower it will end up running.
2) Don't use any of the game options that create new civilizations. These include the one that lets barbarian cities become civilizations and the Revolutions option (which does not work well anyway)
3) Turn off storms, if they are on. This is in the BUG options, probably on the 2nd or 3rd tab (don't remember), not the game options, so it can be turned off in an already running game. In a game which is already in progress this will stop new storms from forming and the existing ones will, eventually, go away.
The 1st and 3rd are likely to have more effect than the 2nd in the long run, although the 2nd can have a considerable effect if there are one or more isolated land masses that start with no civilization on them. Extra civs in such places from barbarian cities turning into civilizations can require quite a bit of extra processing.