How to increase mosfet switching speed, and decrease switching losses?
Either choose a better MOSFET or use a push-pull driver like this: -



Notice that this chip uses identical MOSFETs in the output stage. Here's another using the FAN7842 from Fairchild: -



You should also make sure there is enough deadtime between one turning off and the other turning on.

Both devices can be used to drive single MOSFET outputs if needed. Here's one that drives a highside MOSFET: -



Avoiding P channel devices will earn you a couple of percent more efficiency (genralism alert). This is a useful set of images to give other ideas.