At the beginning of each level, you should try your best to fulfill all missions.
Once all three eggs are on the screen you should do your best to form a group with them as quickly as possible.
Sometimes it's easier to create a group of three eggs by earning a fourth egg. It might be easier to simply clear groups of birdies until the eggs are positioned well, rather than concentrating on only the eggs themselves.
It's best to form groups of birdies at the bottom of the screen as they sometimes cause chain-reactions.
Try to clear big birdies and electro birdies as quickly as possible.