Best way to get rid of mice?

ok i moved into the 2nd floor of a duplex about a year ago and after looking around we found adead baby mouse in the attic on the step and there is powder mouse poison over all the vents and things but i never thought anything of it up until a few months ago i heard a mouse eating and running and lkately i could swear i feel them moving and scratching in my mattress i haves spring traps all through my room as well as poison and 2 diy traps but this morning i came home to find one triggered and about 3 feet away from were i put it with nothing in it do i have rats too??and what is the best way to get rid of these pests any answers would help