when you do a front side air, you need lots of speed, then you have to find the section where its like vert, then if you have enough speed, you kinda go up to that section then pretend like your on a skateboard and ollie, pull up your front leg. Thats kind of how i do it, i couldnt really explain it well.
just be looking for it when you have mad speed and a good section. dont look for it on everywave, pump for speed and to time it right so you make you bottom turn right before the section go real vertical like your gonna extend a vert snap above the lip then throw you hips to extend the tail over and down the line a little.... Good luck. It just takes time and practice....
before y start doing full blown airs learn how to air out the back it its gonna close out. just get alot of speed and make a strong bottom turn that doesnt kill too much speedand pop when you hit the lip