First: If battery is more than two years old, and hasn't had a mid-winter charge put in it, you might need a new one, although a slow charge overnight might just get it back to work!
Second: A new spark plug wouldn't hurt, especially if it hasn't been replaced recently.
Third: Fresh fuel will help, too. If the gas is last summers, and you used fuel stabilizer in it, it should be ok. If you didn't use Stabil, or the gas is really old, that might cause a problem.
Fourth: Check the area around the engine shrouds, for mice droppings, and shredded paper. If you see any of that, then remove the shrouding and clean out the mouse nest!

I'd agree the battery may need charged. It's not unusual for a battery that sits all winter to lose its charge.