I used to be in one such group which operated a Piper Dakota. The rule was to leave the aeroplane on Tabs, which was fair enough as this allowed for decent range and loading. The next person could always add fuel. Got a bit more complicated when we had the TB10, this had to be left full which in turn could have lead to problems with W&B.
Our group now operates a Wet rate. Any fuel bought away from base is refunded from the hourly costs and we have an account at the airfield that any of us can use. Much better way to do it as it doesn't matter how much fuel is left in the tanks