I will sometimes use a sink tip line in rivers early in the year when fishing for smallmouth bass.
1. For the most part you do not need a long leader. I normally keep mine at 4' or less.
2. You can fish just about any unweighted or weighted streamer that you want. If it is too heavily weighted and depending on the depth of the water you are fishing you may get hung up.
3. When casting, I tend to open my loop a bit and fish down and across.
4. Depending on the length of the sinking tip, you may want to retrieve you fly in until you get to the point where sink tip meets the floating part of the fly line. Or you can do a dynamic rool cast and shot the line back towards your target.
5. I never use a sink tip rated more than what the rating of my fly rod. In other words if I am fishing an 8wt rod then my sink tip is rated for an 8wt.
Good luck and have fun!
" If a man is truly blessed, he returns home from fishing to the best catch of his life." Christopher Armour