How do I get control of proportional edit size?

Every now and then, seemingly for no reason, I’ll switch on proportional editing and the influence will be huge, several thousand BU’s. It will come back if you spin the scroll wheel the right direction (mmm now which way is it ???) for 2 minutes but there must be an easier way. Anyone know how? (tool panel control gone missing in 2.53)

You can increase/decrease influence area by shortcut Alt-Num+ , Alt-Num-.