yo tdagg! I aint no pro but I do have my freestyle kit dialed in and squared away
I think anyway...
1. old formula fins make great freestly fins when done right. If not that, just use what ever fin you have laying around w/ the same box type that you'd be willingto sacrifice for the cause. When picking a fin however try to avoid fins with a super wide base. I might be wrong on this, but i've found that if a fin is to wide when cut down, it feels really slow and draggy.
2. having long harness lines helps out almost everything. Its not for early plaining though, if you want that pump! You'll need to sharpen up thoes pumping skills for freestyle, especialy w/ micro fins. The longer harness lines alow you to lean farther forward over the board more and off of the fin when going up wind. When going broad, it lets you keep the sail more up right.
2. Depends on the conditions. in marginal/ gusty wind go with power over anything to make the most out of it. If powered then go ahead and crank on things. You'll want to rig the sail so that it will balance easily everytime however. Ovoid too much outhaul as this makes the sail feel vary twichy. I tune my sails so they feel stable with power, but so that neutrelize easily without to much back hand pressure either. For mast base settings i'm still getting a feel for, but I do know this bit. If set alittle forward you gain a bit more arial control. I just put mine in the middle because thats how they are tested in R&D. If you are using a sail that is samller than the recomended sail range then put it a little farther back if you want. What can happen is that a smaller sails draft might be set to far forward for comfort, making the sail like its pulling offset from your stance. Its a preference thing mostly though.
When going for moves sail in waist deep water to save energy, and limit your sailing area. Make yourself start at one spot every time, plane out as fast as you can, get up to speed, and pop your move. No matter the out come turn around and go back to where you started and get ready to do it again. Don't go for the super hard moves every time either. start doing trick gybes and tacks. Do 360s of every kind. Try jumping over to the lee side of the sail on a full plane! Try sitting down on your board full plane! Get your heli tacks down like a pro. Throw a shaka into everything for more style points. Smile!
The more freestyle you do, the more fun you have. So just go out there and do it no matter the wind!