Prep time is the stage where most of us spend the most time.
It's often the easiest to hack, though. Preparation is key if you want to cut down on kitchen time.
Things I do:
Don't just brown the beef I need - I usually buy ground beef in the big family packs. I used to just do a little at a time, but now I brown the whole package and use what I need, freezing the rest.
2 cups of cooked ground beef = 1 pound uncooked.
So to make best and easiest use, I freeze a pound's worth at a time.
I would not have believed the ease at which one can assemble a casserole when the meat's already cooked, and it's fast too.
Save the gravy - Use ice trays to freeze the leftover gravy for use in flavoring or thickening later. Once it's frozen, pop the cubes out and store in freezer bags. This also works for wine - good use for that end of bottle.