Dynamic Tuning is explained in Dennis Conner's book, Sail Like a Champion.
First you tune the rig to specs, generally 12-15lbs on upper shrouds, 15lbs on lower shrouds, and 10lbs on foestay. Backstay is used to bend mast to point better, or slack-off downwind.
Take the boat on a 10-15kt day, go from a close reach to a beat. Observe the leeward shrouds for slackness and tighten them just until the slack is gone. Remember how many turns you had to make on each shroud. Change tacks and do the same thing on the leeward side. He then recommends doing the same thing in 15-20kt winds.
When you get back to the dock measure the distance from the top of the mast to each shroud, using your main halyard. Make sure they are all equal. If they are not then you must make them equal by re-checking the tune and making adjustments accordingly.
Take her back out and repeat the process. It is a lot easier and faster if you make your distances equal with proper tune before you go out the first time.
Depending on your rig, you may have to sacrifice tune to get an equal distance, but not by much! Warning: don't overtighten rig to get equal distances. If it comes to that then the mast is not stepped on the c-line of the boat or your shrouds are of different lengths.
s/v Pirate Soul