I'm not an expert, but I was told that it takes a good 8 to 12 hours to charge up a golf cart if it's really run down. Not much is going to happen if you plug in for an hour while you are at Outback or somewhere.
As others have said, the gauge or volt meter will give you a good clue and there are a few different types you can choose from to have installed. (although ours is not street legal, we had a street legal speedometer, odometer and charge indicator added to our golf car.)
When our meter is about half way down, it's time to head back home.( the odometer shows how many miles we have covered) I should mention that our gauge seems to deplete a little quicker on the last half.
Our cart is now 10 months old and we have 2100 miles on it. We have gotten up to 56 miles on a charge, but don't typically try for this.
Running it at 30 to 35 miles between charges gets us wherever we want to go easily, and I'm told by our dealer this is the better way to run the batteries.
P.S. After being on the car for 35 miles at a crack, it's time for me to take a break anyway!