soft field take off:
let the airplane get off the ground as soon as it can, then try and keep it right over the ground (10-20ft) until reaching Vy. This will most likely require some slight forward pressure as the airplane accelerates.
soft field landing:
try less power and maybe more back pressure
short field landing:
if you are consistantly landing long of your aiming point DONT CHANGE ANYTHING, just aim shorter on the runway. (maybe the beginning of the first centerline stripe)