A key thing to do to ensure that your bait is lively and enticing fish is to check and move your tip ups and traps.  It sure seems that a tip up checked regularly catches more fish than the ones that have been just sitting there.  It could be that the minnow is getting jostled into more motion, or it could be the simple act of moving the bait up and down a bit to entice fish.

Often when I am tip up fishing with my buddies we take turns making a "drive" from one end of the tip ups to the other.  Think of it as similar to pheasant hunting where you are pushing the pheasants to the end of a field in order to get them to flush.  Now obviously you are not driving the fish the same way you would a pheasant, but if you are checking your traps while making your "drive" it does seem to help.  I know it has increased our ice fishing success when using tip ups.