1) Shoot as many in a row as possible. 

2) Only upgrade your gun to level 4. Even on 6, youll still have to shoot the black ones twice. At least this way, you save money. 

3) Buy the complete set of droids - then, when you are damaged - you get repaired quickly. 

4) If you know you wont have time to shoot a particular fuzzle, collect the bonus. Youll still get loads of points! 

5) Only get the bombs that are coming directly towards you. The rest won't touch you - and theres a risk of missing, and losing your bonus.