[brucepick]

Yes I agree with what's already been posted:
Circumferential grooves will be better than crosswise grooves.
'Performance' tires will likely have higher rolling resistance to get better traction.

Also pay attention to the tire's weight (you can see weight in TireRack specs). Rotating weight is supposedly 3x as harmful to your mpg as non-rotating weight, which is why people bother looking for lightweight alloy rims.

BUT here's what I did when I bought tires nearly a year ago:
I made sure I got tires rated for 44 psi, and not 32 or 35 psi.
If I'd had the money available I might have gotten tires rated at 52 psi.

I dared to run my old 35 psi tires around 40. I run the new 44 psi tires around 52. I don't think I'd want to run 35 psi tires that high. The increased pressure really helps fuel economy.

A few years ago there were some efforts to get specs published for all new tires, showing their rolling resistance. Big business (that's Big Oil) and government got together, and made sure that legislation got killed off. If you're reading this in the USA, be sure to vote this November!