During development the best way I think is to get in touch with your friends, post some facebook messages etc, to borrow some devices, or get such friend to meet for a beer and try to run your game on their devices. Or buy one. Test it as much as you can, because differences between android devices are far more unpredictable as you might imagine.
This. There are a LOT of forums dedicated for testing, just sleuth around. The model is generally, "Test my game and I'l test yours!". It's very useful and it works because everyone is happy.