Planing a fishing trip

Me and my buddies are trying to plan a trip to Erie for steelhead this September I went last may and had a blast if any one could help and let me know when would be good weekend to head up there it would be greatly appreciated

If you've only got one shot for a trip this fall, I'd go in mid-November.  
 
If you're set on September, it's a toss up.  That early in the year a lot will depend on how much rain we get.  Like Skip said, later is generally better. 

I wouldn't even consider going in September.  October is when I start thinking about it, usually make my first trip in the 2nd half of October, and November is when I try to make it out every week.
 
In September there might be a few fish at the mouth of the creeks near the lake, but you'll have every fisherman in Erie confined to a small area at the very bottom of the creeks shoulder to shoulder with hardly any fish in the middle or upper sections of streams.