Additionally, you want to make sure that
Once you have the tension set that when you are trimmed up and sailing, that the leward side of the boat does not have any slack in any of the rigging on that side of the boat. If you have slack in the shrouds, then they are not tight enough. As Ken has referenced the Loos gauge, it really is the one true way that you can actually take the guess work out of adjustment. They supply excellent information about adjusting the standing rigging and stress the importance of not having slack in the downwind side of your rigging and what can happen unexpectedly when you do have slack and how detrimental it can be to the rigging as well as the structural integrity of the hull and its' strength if something inadvertantly were to happen due to unforseen wind shift. Basically, what you want to do it determine the specifications of the rigging or the shrouds. The diameter and the number of strands that are twisted together are going to determine the yield strength or tensile strength of that cable. The Loos allows you to determine with precision the amount of force or tension that is being exerted on the cable. Loos doesn't recommend going much more than 12 to 15% of the tensile strength of the cable. Sounds like if you don't know someone that has a Loos, you may want to consider buying one. Once you get it and read their documentation, then do it, you will know a lot more than you did about it when you posted this question. Then, you can talk to your friends and offer to adjust their rigging for them for a small fee. You are going to know way way more than they do and you can recoup your investment in the Loos. What you do not want to do is think that you can adjust the tension by tightening up on it and pinging the shrouds like you would ping the spokes of a bike to see if they are tight enough. Especially when you can get a precision instrument for cheap and save the cost of having improperly adjusted rigging that could have a permant detrimental effect on the rigging and the boat.Rigging adjustment is an art and yet not all that difficult with the use of common sense and the use of a gauge and or the recommendations of those with experience. You may look here in some of the archives, since this subject has been previously discussed.Also, check out "The Complete Rigger's Apprentice" by Brion Toss. You can find it here on this site and it is good reading as well. There is a lot out there about rigging, just geegle it.