Work from the bottom
Look for matches near the bottom, preferably vertical matches. This maximizes the chances of cascading matches, clearing more jellies in a single move. The exception would be if you can utilize a power candy.
Work one side of the board at a time
Focus on one side of the board at a time. It's easier to plan your next move if you only need to think about half of the board.
Plan your next move
Always plan ahead. It's a great way to take advantage of a lucky set up.
Shoot for two jellies at a time
You need to clear more than one jelly at a time to beat level 33. Cascading matches are a great way to accomplish this. Power combos too.