Just run the saw the way you normally would except don`t rev the **** out of it out of the cut for the first tank of fuel or so. After that keep on operating as normal. After rebuilding many hundreds of saws and discussing this scenario with dozens of other saw mechanics we all seem to agree that operating the saw normally from the outset will allow for the best breakin. Some think the carb should be set a tad rich to provide extra lube and cooling but I personally just set it the way it should be operated and let it go to work.
Tune the carb with cuts in a big enough piece of wood to load the engine, fourstroking while out of the cut and cleaning out and pulling hard as soon as the chain bites good into the wood, you will never have a lean running saw doing it this way. Tachometers are good for stock only saws and getting them to a fairly safe performance level if there are no other issues affecting the engine like an air leak.
