Gas gauge fail

My gas gauge started reading low. Went to go get gas. Only took a few gallons and now not moving off of E. Any direction where to start?

We need the year of the car for starters. 55 and I believe 56 used a King Seely (sp?) type gauge, different from 57. That's your starting point. My 55 has an access panel in the trunk giving access to the sending unit. I'd start by checking the connections and especially grounds there, then move to the dash. The fact that it happened slowly also makes me wonder if the float sunk, ie filled up with gas. I'd have a new gasket handy before I pulled the sender, the old one will probably fall apart and leak. If it's full of fuel, remember that if you get tempted to solder it up.