Gravy help!

I am looking for advice on how to make a nice thick turkey gravy. I used to do it like my Grandma taught me and it always turned out great but over the years I have lost that touch and it comes out too thin and watery. When I add flour to thicken it up, it just ends up tasting like flour and losing the gravy taste. I know there is a technique with the heat to get it to thicken up right but can't recall how to do that. Any helpful hints from all you great cooks out there?