When measuring, the old adage "measure twice and cut once" can be excellent advice. Pros, however, have their own variation; they usually only measure once, but then will read the measurement twice. They will mark the cut line, then cut the wood just so the saw kerf is touching the line.
When setting up workbenches, the height is generally figured at about hip pocket high. But before you buy or build a workbench, consider the height of your tablesaw. If the bench is the same height as the saw it can then be used for extra support when sawing over-size materials.