Two or more networks in range...

When I was in my dorm at college, or whenever I'm at the mall, my iPod connects to the first WiFi connection available. Every time it does that, I end up having to change it to the correct network. When I'm at home, my WiFi service comes from 'xfinitywifi' (which happens to be available around my dorm too), and when I'm at the mall, there happens to be a 'Macy's' on one side of the mall, and directly across from it is 'Apple Store' (Macy's WiFi seems to only allow you to check their site...). I was wondering if there is a way to make my iPod Touch select my personal WiFi router and 'Apple Store' instead of connecting to the first one it finds? I know that its possible to do it on a Mac (under 10.6.8). so, there has got to be a way to do it on my iPod Touch... Thanks