I feel really miserly never offering to buy anyone a round at the pub but as a non drinker I can only really manage 1 or 2 drinks, sometimes I only have water. What usually happens with me is I either get my own or someone offers to buy a round, I'll say I'll get my own and they insist on including me so I'll then offer to buy that person I drink later on.
What does everyone else (who doesn't drink) do?