Tensioning has been discussed before but no there should be no slack in the shrouds.
The first thing to do is lossen the shrouds and then take a line or measuring tape to the main halyard and raise it. Check the side measurements to insure the top of the mast is in the middle. If not, then tensions the upper shrouds to put the top of the mast in the middle. Then equally tighten the shroud turnbuckles until you get some prebend. With some weight attached to the main halyard, see if the prebend is about 3-4 inches from the back of the mast to the line where the boom generally is attached to the mast.
Then take the lower shrouds and first straighten up the mast long ways up by sighting up the sail track with your eye. Then tighten equally to take some of the prebend out. Without any gauge, then take your two top fingers without moving your hand, pull back on the upper shroud and if you get about 1-2 inches pulling back, then you are in the ball park.
Then sail and check the shrouds.