Let me preface this by saying that I’m an excellent cook, and we eat very well at the Pad of Evil®. I don’t want to incur the wrath of Zenster, here. 
But let’s face it, prepared foods - be they fresh, in a can, or frozen - have gotten better over the years, are ubiquitous, and part of the lifestyle of many. However, I am hardly ever satisfied to cook and serve the foodstuff in question as is; more often than not, I’ll “jazz it up” with other seasonings, sauces, and so forth. I’ve found that I even tinker with muffin mix, as I’ll describe below.
Frozen pizza.
There are good wood-oven thin crust pizzas out there, as well as rising-crust ones. At the Pad of Evil®, if there’s pepperoni on the pizza, we move it all to one side, because jeremy evil doesn’t like it. I add onions to my side, as I believe pizza is incomplete without it. Extra grated mozzarella cheese is de rigeur, with perhaps a sprinkle of Parmesan and Romano on my side. And even a drizzle of extra-virgin olive oil before popping it in the oven. Heavenly, fatty goodness.
Pasta sauce.
I don’t always have time to make red sauce, so when I buy a premium brand plain tomato and basil sauce, I’ll add to it as I heat it. Pepper, more herbs, a splash of balsamic vinegar, and swirl in some extra-virgin olive oil for that velvety texture. A pinch of sugar is also good, as I like my red sauce on the sweet side, as is a quick squeeze of lemon juice.
If I’m adding ground meat to the sauce (again, this is when I don’t make it from scratch), I’ll add most of the above, but include red wine vinegar to give the meat that quasi-Bourgignon quality. (In the past I would have added actual red wine, but there is no alcohol in the Pad of Evil®. And I know that wine vinegar has an alcohol content. You know what I mean.)
Canned vegetable-type soups.
When we’re broke and desperate. A few splashes of Worcestershire sauce - or even a dash of HP steak sauce - goes a long way.
Chicken casserole.
Aside from cooked, cubed boneless chicken, the rest of this is entirely from prepared foods: a can of cream of chicken (or mushroom) soup, premium frozen vegetable mix, and topped with Stove Top® stuffing. A dash of curry powder in the “soup sauce” adds a surprising accent. Grated cheese overtop, with pats of butter dotted here and there, sends this over the top. It’s along the lines of chicken divan, but since Jeremy doesn’t like broccoli, this is a reasonable compromise.
Muffins.
It’s much more economical for me to bring muffins in to work, rather than buy them at $1.15 each, so I buy Quaker muffin mix. I buy the low-fat variety not for the low-fat reason, but because the regular variety requires eggs. (We don’t always have eggs in the house. I avoid them because of my high cholesterol.)
My favorite is the low-fat carrot mix. To half of the package, I add about half a teaspoon of baking powder. I think that makes them a bit more fluffy. I also stir in some brown sugar and cinnamon, breaking up any lumps as I go. Finally, I add about two tablespoons of melted butter (I said it wasn’t for the low-fat quality that I bought the low-fat variety!). I stir in just enough milk (instead of water), and then add about half a cup of sultana raisins, tossed in flour so that they don’t sink. (Although they don’t really sink in muffin batter, but in cake batter, but it’s oddly satisfying to toss raisins in flour…)
Montreal Steak Spice.
An extremely versatile rub and wonderful addition to any marinade. I must try the chicken version!
::sigh::
I could go on and on… but my muffins are done. So how do you “jazz up” prepared foods, to make them a little less boring?