Okay here's my advices...
For Fisheye/wide lense filming; I'm pure 10mm user. I'm always trying to have as small number of markers as possible. Easy way to do that is film your stuff first and then test, which markers are unuseful.
Another tip to make your wide lense filming look better is NOT trying to keep your skater centered in middle of screen all the time...let the camera "live". Watch some real life footage to see what i mean.
I think theres no real mm's that people use in Long lenses ? I have heard that someones have some mm that thei're not going bigger anymore...like someone said that he don't ever go over 300mm.
I don't use 500mm so oftenly...i have probably used it three times in skating footage. My advice for long lenses is to use mm that you feel like best.
I don't have so many advices for ramp slows. Basic ramp slows for flip tricks and gaps are pretty easy to do. Just put one marker right when you're popping your trick and another marker right before you're landing your trick. These two markers should be "100%" markers (speed i mean).
Then you just put marker into middle of these two and set their speed to whatever you want. Personally i like to use slowest or second slowest one.
When filming slides or grinds you can use more imagination with ramp slows...like ramping down when starting a grind gives you nice sound effect and little extra kick and ramping down when you're landing makes you're trick look sicker imo.
And also Roll in's and -out's. They make your footage look better. Personally when filming line or fisheye footage i stop my camera always when your skater lands the trick. I got that from my real life filming and i think filming in skate is much easier if you have filmed skating in real life =)