I find it's a bit like parallel parking. If my starting position is good then I only need to make small corrections. A good first skill is estimating the distance between your trees in order to decide the height of your straps. It just takes some practice.
Last week I hung my BB a bit too tight, was sitting camp seat style thinking about resetting one of the tree straps, got to talking with a friend, the next thing I knew it was 1:00am in the morning and I had fallen asleep with my head in the footbox end of the hammock.