You can narrow down the selection by having a look at the alcohol content. If it's a minimum of 13% it means the grapes were picked with a fair level of ripeness. This means you have a better chance of getting a satisfying tasty amount of fruit flavour.
My long held theory was reinforced by visits to a couple of expensive convenience stores in Avignon, France recently. I didn't expect much but I found a different Cotes du Rhone in each store. Both weighed in at 13.5% a/v. They were both under 5 euro and were really tasty little wines.
Of course you'll find great reds under that level and some undrinkable stuff if the alcohol level is too high. But at the budget end of the market the 13% mark is a great help.