[Justin Stiltner]

You might try lubricating any sliding surfaces. If you reduce the diameter of the drum used to take up the cable you will effectively increase your gear ratio. Also look into different ways to string your cable to give you mechanical advantage. You can ease the load on your motor by providing counterweight that works to pull the lift up at all times. This may be an actual weight, or preferably springs, penumatics, or other springy like device to help your motor out.

Also look into loosing some of the weight of the part that moves up and down, weight up high is nearly always a bad thing!