Over-inflation is what causes air-beds to pop at the seams, so it is best to under-inflate just a little to give it some wiggle room. If you are alone, sleep in the center. If your gf is there, sleep equal distance from each other on the sides so that one side does not rise higher than the other.

Am i best to over-inflate or under-inflate ? by bump i mean after a while the air bed pops at the seams it appears and forms large bumps that make the bed un sleepable i have got a new one arriving and i'm hoping to do my best to avoid it happening again.

It is a double size and i sleep on one side and my gf sleeps on the other side some night but most nights i am in it alone and tend to lie on my side, should i be lying in the centre to avoid putting too much pressure on one side also ?