^^^
there are already many threads about the 50-50 method, but generally it is the easiest to do, esp. for beginners. this is my preferred method because i hate freezing milk and adding the lye bit by bit thing.
are you planning on using fresh or powdered milk? if using the powder variety, you can make a high concentration, at the end it'll be just the same as using a full liquid swap.
i personally see no big deal doing full liquid swap vs 50-50. some say doing 50-50 = not a real milk soap, but i disagree.