Jon,
The previous two posts are pretty much correct - shaking the can is very important for complete paint/gas mixing, and heating the can is very important as with the perfect gas laws, increase in temperature means increase in volume of the gas, which means a higher pressure inside the can, which means a greater atomization effect for the paint.
Always try to paint outside on days with very low humidity, and a rather low temperature differential between the outside and inside - if you paint outside and it's cold, then bring the painted object inside, it's like walking inside to a warm room from a cold outside when you're wearing glasses - what do they do? They fog up.
This can cause "blooming", or slightly discolored patches because of the humidity.
All this means you might need to paint only when the conditions are perfect, or why not try to make or buy a spray booth - they take the nasty fumes and vent them to the outside. I use one and we never smell anything inside.
Cheers,
LeeTree