It depends on certain things if you'll need a swap file or not. If it's a laptop and you want it to hibernate or suspend you'll need one if not most likely don't given enough ram.
but the rule of thumb as always be 2x the amount of ram for a swap file. thus if your machine has 2gb ram make swap file 4gb.
you can use the mint livecd to make the files if this is your first install of mint I would suggest that you just allow it to automatically partition the drive for you.
if you want to custumize the partitions you can do so but seleting other when the partition page comes up
good luck and happy computing.