It has been a few years since i was spotting there but i know of a good spot just off Lindberg Ave. I cant remember the exact road but it is a service road that runs just along the permiter fence on the northeast corner of the airport. With this view you can see most of 12/30 left and right. A while ago there were more heavies into STL with TWA's 747's but now all you will see is TWA's 767's and maybe a few charters, or freighters. Like I said its been a while since ive been there maybe someone else can add to this.
The Lindberg Avenue road location is excellent for spotting -- right at the end of the runway. Get on I70 West past STL then exit on Lindberg turning right (I guess thats North). The parking lot will be about half a mile on your left.
Not much heavies however but there's quite a lot of traffic.
Hey, I know of some good places to spot. the lindberg parking area isn't too bad but there is an awesome spot that i know of. You go down lindberg and turn right at th boeing girft shop (awesome place) and you stay on that road forever. you will pass the 57th sqadron restaurant (i am not too sure of the number) and the road takes you to the back of the UPS aircraft parking area and then you will come to the edge of runway 30L and 30R. it is a great place to sit and watch planes. there is no designated parkign area but you can pull off and sit there. it is awesoem there. e-mail me if want. propilotJW@aol.com