slop free linkages:
remember the linkage assembly is only as strong as the weakest part, and will have all the slop of all the links put together.
-keep linkages short (tail servos!)
-slop free servos
-heavy-duty servo arms
-sullivan or other metal solder clevises soldered to 4-40 rod, end threaded
-another metal threaded clevis on the other end, loctite in place when linkage is set right, use the blue loctite, not the red!
-and make sure that you use decent control horns, too.
one nice thing about the metal clevises (plastic ones too) is that for most standard and mini servo arms, you'll have to open up the holes to fit the clevis' pin, do this carefully and there will be zero slop.