A good framer can ease the finish carpenter's job by providing plumb walls and plenty of blocking for nailers for attaching trim. But even if the framer couldn't read a level and and even if he added no more blocking than was absolutely necessary, the finish carpenter's job is to make the doors, windows and cabinets work, and to make the house look good. Finish carpentry is more than interior trim. Rough carpenters evolve into finish carpenters by learning how to measure, mark and cut more accurately. With practice, splitting the pencil line with a sawcut and working to closer tolerances become second nature.
Perfect miters are only part of finish carpentry.
Finish carpenters must develop an eye for proportion and detail. They must learn to visualize the steps that lead to the finished product. I teach these skills to novice carpenters at the Heartwood School in Massachusetts. To make learning them easier, I've organized the following ten rules of thumb. It is usually more accurate to hold a board in place to mark its length rather than to use a tape and involve numbers.