What time should I lineup to get the Iphone 4?

i didnt make the preorder list so i am going to try and get an iphone 4 by walkin on thursday. I have contacted the att store near me and they say they will have 40 total so 20 32g and 20 16g for walkin customers. What time should i get there in the morning I was thinking like 5 or 530 but do you think earlier would be better, and also me and my friend are going to stop by radioshack first on the way there. Which do you think would be better to go to. Thanks!