Welcome to Slinging.org Justin.

Trial and error... I made chainmail using that and it's definately better suited for slings . Your sling sounds cool. How long is it? What slinging style do you use?

I still haven't quite figured out the overhand style . Do you extend your arm out (i.e. over your head, behind your back, etc.) or do you keep it more or less stationary and use your wrist to twirl the projectile around? ???

Have you tried doing figure 8 style? It seems completely absurd, unnatural and inefficient at first. It took me forever to figure out, but it's so fun that I'll go through the motion of doing it even when I can't sling (usually between classes).

I tried the underhand and overhand (I had a short sling) and I couldn't seem to keep the sling going for any more than 1 full cycle (sometimes less) before I messed up. I recently realized that prehaps I should be using my wrist and not my entire arm...

The best/only way to figure it out is to watch it. Basically the idea is to get your hand bent over/behind your back so you can fling the sling in the same fashion as a catapult or trebuchet. I don't want to even try to explain it, so just watch these videos over and over until you get it. They look crazy, but if you get the hang of it, it's rather natural.

Normal Throw: http://www.altay.vilko.net/dl/sling/BasicThrow.avi
View from back: http://www.altay.vilko.net/dl/sling/HeadShot.avi

these aren't my videos... I forgot where I got them from and I can't seem to relocate them, so I just uploaded them to my website.

all i can say is look closely to what the fella is doing watch it over and over again And watch it Slooooowly that really helps 

There they are! I looked through the articles section, but I only looked at the ones that said they had movies on them. For some reason it doesn't have the little movie clip icon for that one...