I use the Red and Green felt thingies, they work for me and act as an added reminder which is Pos and which is Neg.
Off topic but, I'm beginning to think it strange (in a good way) that it seems I never seem to have battery problems!
I mean, the battery in my 85 Toyota PU dates from 2001, the Matrix battery is OEM 2007, the battery in the Triumph Spitfire is a $9 U1 Walmart Lawnmower battery from 2005 and our Lawnmower has the same battery, bought at the same time.
All work fine and I never touch them.
What am I doing right?