Hike on some of the weekends. During the week, bike for an hour, or run for half. Or change it up. (or do some other aerobic workout.) Start out slowly so you don't burn out. Increase the amount of time you spend working out closer to the hike.
Do a strenuous hike in the week before your hike.
Plan to acclimate for (at least) 24-36 hours before you start your hike.
