Spend the first few levels familiarizing yourself with the game's physics engine and replay them a few times until you get the hang of bouncing your shots off the walls. Perfection of these abilities will help in later levels.
If you see fans in a level, it's not a bad idea to shut them all off and take a dry run to see where your yarn ball will - and won't - go. This will help you determine which fans need to be turned on when.
You can rotate pipes when the yarn ball is shooting through them - don't be afraid to experiment with them throughout your playthroughs.
You'll need to either earn stars or use the in-app purchase that unlocks every level immediately.
Your star award is dependent on how quickly you solved a level, and how many attempts it took you.
Once per hour you'll be able to hit the light-bulb icon at the bottom-right of the screen to get a solution.
If you want to use the hints system more than once per hour, you'll have to purchase the option through the in-app store This costs $0.99.