I have only been using a spinnaker with my cat for about 6 months and feel like a complete novice. It seems like every time I go out, I figure out (the hard way) what to do, or not to do. I would love to learn some of your "Do's & Don'ts".
Here are a few random ones of mine. I have a Nacra F18 with a front snuffer, so that is my perspective. Obviously, different boats or snuffer systems will have different issues.
1. When dousing the spinnaker, if I sail close to straight downwind, I almost always run over the spin sheets with the windward hull. It is really a pain to clear the lines after that. I need to be a little upwind when dousing to avoid this.
2. Rather than trying to see if the spinnaker is raised up to the proper height, I have marked my halyard so I can easily see. Because my halyard is blue, a marker would not work. Instead,I just used a needle to thread a couple pieces of sail repair thread through and tied them off. I can easily see the thread and they do not interfere with the pulleys.
3. When solo sailing and using the spinnaker, its hard to give your forward hand a rest. I have found that I can free up my forward hand for a rest or other needs by positioning the tiller extension a certain way. I put the tiller extension behind my back and hook onto it with the inside of my rear elbow. With this arrangement, I can very effectively steer by simply twisting my upper body. My rear hand can hold the spin sheet, giving my front hand a rest. Try this if your are solo sailing...it works.
4. Apparently, it is important to use your mainsheet as a backstay when sailing with a spinnaker. I think this is an important matter that should be more widely publicied than it is. I understand that its possible to damage your mast if you ignore this issue.
Here are some questions I have:
Can you trapeze when solo sailing a spinnaker? This is something I have not tried. I have trouble seeing how to secure myself to the boat during this point of sail while hanging onto the tiller extension and spin sheet only, especially with course changes necessary to react to the gusts.
How do you avoid snagging your spin when dousing? I seem to get a high percentage of snags on something during snuffing. By this, I mean not only the hull running over the sheet, but also internal snags in the sock, etc.
How do you tell if your halyard is too loose or too tight?
What's the best way to jibe a spin? There has got to be a better system than mine.
Steve
First one; Don't sail dead down wind when dousing the kite, try and sail a little hight, also; stand on the sheet as you trip the halyard so that the sheets don't fly forward - I sail my 17 with the kite and have added cleats to do this (also allows me free hands to do other jobs too)
Forward hand rest; difficult one, I sometimes move the sheet to my aft hand for a short time.
V important to keep mainsheet tension and let the Downhaul off.
Trapping with the kite up is a scream (and makes good VMG most of the time too); Get back into the foot loop(if windy enough) and go for it !
When you say you are snagging, is this on the kite front ect - this may be cured by keeping some sheet tension on ect; of the kite in snagging on sharp edges then you just need to go over the boat very carefully and remove them all.
As for the hoist height; pull it as high as you can for a full shape; let it off a little to flatten it !
Gybing well is very dufficult on your own;
My method is to :
1, iniatiate the bear off as I come in off the wire
2, ease the sheet a little as I do
3, grab the new sheet on the tramp and try and keep the old to hand and tidyup any loose
4, main goes over and I sheet in PDQ on the new sheet dropping the old - with a bit of luck the kite pops around the front, and you sheet in (steering as well) and off you go
5, ,Hull comes up and out on the wire...
in theory 
