for nollie/sw heels-
your pop foot should be straight (i see a lot of people point thier feet, but this leaves you with less pop and more mob possibility i think) with your pressure on the tip of your foot on the heel side. keeping it straight across the board (also, try not to curve this foot either) curl your flick foot's toes over the edge of the board and as soon as you hear the snap of the nose flick that foot straight at the nose. your ankle should roll right up to the tip and flick it out. the rest is just getting the catch/land part down which shoudlnt be too bad.. as far as how close to put your feet, the trick is to put it low enough to get good pop, but high enough so you can go fast and level it out. i find it to be the best like an inch behind the bolts, but you'll see when you try it where you feel comfortable. i really hope this helps for these, cos they are the two best tricks ever once you get em working, so get ready to have a blast once this lil learning period is over.
not so great at these, but for nollie noseslides always remember to keep your shoulders straight! such a little aspect but it helps solve the problem of locking in and just stopping (my problem forever, i used to feel stupid even trying them).. you keep em straight and you'll have to worry about sliding too much if anything, which is always better. it took me forever to figure out nollie crooks (i feel like im the only one who had a really rough time with this!) and in the process figured that little tip out about the noseslides. i hope that helps you out a little
this all prolly makes no sense, i think its pretty hard to type how to do a trick and have it come out coherant haha.. but hey hopefully it helps.