When you're almost at the dismount for the lift, sit sideways and have your board pointed straight.
Wait for the chair to bring you to the ramp of the dismount, don't get off too early or you'll be in the flat spot. Once you're at the ramp of the dismount, get up and push off the chair with your hands making sure your unstrapped foot gets onto the inside of your binding so you don't get your leg caught under the chair.
You can also push off with the free foot but using your arms to push off the chair should be enough.
Final tip is to go straight! Don't try to go sideways and slow down too early, that's what will make you fall. The further away from the chair when you fall, the better. That way you don't get in the way of the next chair. Just remember to get that initial push! If you're just being shoved by the chair, it'll just throw your balance. It may seem scary and counter intuitive at first but going slow is worse than going fast. Speed is your friend.