I'm a resident of the state of Michigan but I'm going to school full time (grad school) in Florida. I have 3 W2s, 2 from FL and one from MI. Since FL has no state income tax, do I need to file a return in FL? Also, do I need to declare my FL earnings on my MI tax return?

Any help would be greatly appreciated!

When you attend college (graduate or under-graduate) out-of-state, by law, you are NOT a resident of the state where you are attending school UNLESS you take positive steps to ESTABLISH residency, such as register to vote.

For this reason, you are a Michigan resident and must pay Michigan taxes for the Florida-based income, because all of the states that have a state income tax make their residents pay income tax on ALL world-wide income.