I normally run all my tires at the maximum pressure molded into the sidewalls ... or a few pounds over. (When I'm busy and have someone else service my vehicles, I check the pressure immediately afterwards ... if they've let air out of the tires, I make them take it back into the shop and fill the tires back up.)
Max pressure provides better traction on ice and improves gas mileage.
Wear should be even across the tire tread. More wear on the outside edges indicates under-inflation and more wear down the tread center indicates over-inflation.
Uneven wear on the front tires indicates alignment problems. There's lots of info on the web on how to spot and diagnose alignment problems.
The frontend alignment for my '77 B200 didn't match the book. A friend, who really knew how to dial-in a vehicle, determine the proper alignment specifications for my particular vehicle and wrote them on the frame in white grease pencil. A tire dealer realigned the front end to factory spec's, even though I'd written the spec's in the service order, with directions to follow those spec's written in large, bold letters. The dealer wound up giving me a new set of tires after 3,000 miles because the factory spec's caused the tires to be worn to the plies that quickly. (I pointed out that complaints to the manufacturer and BBB, as well as a civil suit, would be detrimental to his franchise.)
Rear ends can also be misaligned, causing the vehicle to "crab" as it runs down the road. This eats up both the tires and gas mileage, as well as making the vehicle much, much harder to control on ice. Easiest way to check rear end alignment is to measure the distance between the outsides of the axle to a single point midway between the frames towards the front of the vehicle. The measurements should be the same for both sides of the axle.
