How to politely follow up after contacting potential postdoc advisor?
I've encountered this situation recently. My personal strategy has worked well on multiple occasion.

Send back the first e-mail with a beginning similar to this (I suggest you adapt it):
Dear Dr Smith,

I'm afraid my precedent e-mail arrived in your junk mail. Just in case, here it is again. 
Thank you very much for your attention. 

Edit: I don't resend an e-mail after only a week. I usually wait 2-3 weeks...even more !