Ignore objects that are difficult to destroy. For example, skip lockers unless you have activated a power-up that will allow you to damage them quickly. Move to a good position to get the most out of your hits. If possible, move so that you can damage multiple objects with a single hit.
Fire extinguishers
Always hit the fire extinguishers as you enter a new room to get a bonus and free points from the explosion. Always check behind the blackboard to see if other hidden bonuses are present.
Upgrades
Get the "Time Upgrade" as soon as possible. Weapon upgrades should be next, as they will allow you to earn more coins. When you have the choice to purchase an upgrade or a boost, the upgrade is generally the better choice because it is permanent. Recommended upgrades are Party, Speed, Freeze and the Magnet. After reaching level two or three try to maximize them.