I've seen tourists get Bic Camera cards. (I'm a Bic guy). If Yodobashi has some kind of "residents only" rule, you should immediately walk out and go to Bic or Laox.

I'm not sure if this has been explicitly mentioned - you need to make a second purchase to get the benefit of the points you earn with your first purchase. So, for example, if you want a lens and a memory card you pay cash for the lens and then use the points from that purchase towards the memory card. The staff are quite accustomed to ringing up the purchases separately at the till in this way.

Also worth noting - it may be 10% points for cash purchases but usually a lower percentage for credit card purchases.