Start by choosing a modern “hardpoint” handsaw. With its exceptionally sharp, hardened teeth, this type of saw is hungry enough to chew through an inch of 2x construction lumber with each full stroke. Hard-point saws can’t be resharpened, but who really resharpens old-style saws anyway?
The best hard-point saws have a shiny blade. Why is this a great thing? Angle the saw so that the reflection of the wood in the metal is a perfect continuation of the actual edge of the lumber, and you’ll be cutting square to both the edge and the face of your board. No pencil line required.
Take full strokes with your handsaw, not short, choppy ones. When you use the full length of the saw blade, your muscles are happier, cuts go faster, and the saw stays sharp longer.