Not many....other than;
Build a good, solid and STRAIGT jig (yep....some people still have to build these things on jigs).
Keep paying close attention to keeping everything square and plumb during construction. Plumb bobs, laser pointers, etc will come in handy.
Spend a little extra time making sure the main longerons are bent just right, and make sure all the bulkheads fit will. This may and will require some "modification" throughout the build.
Pay special attention to the main side skins where they transition from the main square part of the fuselage to the rounded aft portion right behind the wing attach points. You'll have to cut these skins yourself, and those corners are a real bear. The newer 7/9 kits have that skin finished and that corner is almost a gimme compared to doing it on the -6. Be patient here and it'll pay you back in spades.
Do a good job keeping the seat ribs straight and spaced evenly too, and pay attention to where they attach to the 604 bulkhead, as you'll have to modify some of the ribs to allow for the spar bolts/nuts in the future assembly process.
Don't forget to put the steel spar attach plate in before you finish off that section. It can be a real son of a gun to do later....and....make sure you get the right steel bar in there facing the right direction. All 4 of those things are actually different!
Other than that, just have FUN! They aren't as bad as you might think, and all your friends will think you're building a boat until you pull it out of the jig and flip it over!
I'm sure I forgot a bunch of other stuff, but half the fun is discovering those yourself....
I know after building 2 old slow build RV6's, I can't wait to do one of these new-fangeled prepunched self assembling kits
Cheers,
Stein.