I've been using what I guess is a "triple" surgeon knot for braid to flourocarbon leaders. Seems to work fine and haven't had any knot failures. Haven't tried tying braid to braid yet, so no recommendations there.
When it comes to tying on hooks or lures when not using a swivel, we use a loop knot we learned years ago from some guys catching snook off the beach in Englewood. They were getting 2 to 3 times the hookups we were while free-lining greenbacks, and the only difference we saw was they had a loop knot to their hook and we were using the good ol' clinch knot. I haven't found a good illustration of the how to tie the knot, and have no idea if there's a name for it. You make a wide loop on the leader with the line crossing itself on the side away from you. Then you pass the tag end through the hook eye, bring it around the base of loop twice, then pull the loop over the hook and pull on the main line to tighten things up. When done right, it makes a knot similar to a bowline with an extra wrap. If done wrong, it becomes a slip knot. Very useful, fast to tie once you get it, and allows the bait more freedom of movement with the loop.
Easiest loop knot in the world to tie. Never had one fail and been tying one for years
http://capmel.com/loop_knot.htm
Uni to Uni but with braid you always want to use a lock knot. For braid to mono I use either Uni to Uni or a sebile knot. The sebile is the best for casting by far, no knot in the mono or fluoro at all. I've never heard a bad thing about any of the knots mentioned either. I use whatever I feel the most comfortable with.
I use a swivel from braid to mono it saves time and aggravation and stops the line twist problems......sayin.
