Well, I don't know much about wines at all, either.
But, I do have a couple of rules of thumb.
I use Malbecs when the dish contains a LOT of tomato. Chili, pastas, etc. Malbec (which I generally like as a drinking wine, but I'm not that big on red wines in general) works really well with tomatoes.
In dishes without tomato, though, I find that it takes on harsh tones when cooked. I found that out a couple of years ago when I used it in beef stew and I was not impressed with the results.
For beef stew and other dishes that call for a red wine base I generally go with a Merlot or a Pino Noir, dry reds that have a lot of character when cooked in a dish.
I'm using a Robert Mondavi Merlot for today's beef stew because it's what I have open in the refrigerator, left over from my Christmas cooking. I used it as the base for a shallot mushroom reduction gravy and it was very, very nice, so I suspect that it will work really well in my stew.
I also have a bottle of Alamos Malbec in the fridge. I don't know how long that's been open. I need to pour a glass to see if it's still good, and if it is, make something with a lot of tomatoes. Like chili.