Try to get at least 4-5 flowers minimum, but 8+ is optimal!
There's a pretty easy flower straight off the bat as a barrel will come immediately down the center. Jump off it to get far enough ahead to grab one flower immediately.
There are three distinct kind of "phases" to the game:
Barrels come straight down the middle and you don't need to move. This is the easiest phase, so try to get a couple flowers here.
Barrels start coming down the right and left lanes as well, and at random intervals. The snifits also start moving forward but will stick to their own lanes. Jumping off the snifits gives you a much bigger boost than the barrels, so try to hit them as much as possible!
Barrels stop coming, but the snifits start moving back and forth between the lanes. This is the hardest phase, so just keep trying to anticipate where they're going to be and keep jumping on them as much as you can.