Meg has a lot of good tips - before you move any furniture in go over every room with a fine tooth comb and find every gap and hole that you can and plug it up. Mice only need a space of 8mm to squeeze through so even the smallest crack or hole is still an entry point for them. The only other suggestion is don't have clutter around that they can get into - have toys and everything in rubs with lids and make sure they can't get into your drawers etc.