Some things to consider would be how many rounds a day you will be shooting, shotgun fit, and the price you want to pay. If you plan to shoot clays, plan on alot of rounds going through your shotgun. A semiautomatic will produce less recoil and save your shoulder. Over and unders are stylish but no forgiveness on the recoil. Probably first and foremost is fit. Putting various shotguns up to you shoulder and sighting it will give you an idea of what fits you for sighting down the barrel. Price is also a factor. I have a Bennelli auto that works great for me. Screw in chocks, adjustable stock shims, light weight, light recoil and great relieability.
The Remington Express, as mentioned, would be perfect for a slug gun. Less expensive and figured to be a one shot deer gun. It's tough to pick one shotgun for all occasions. Just think it through and you will come up with the best solution. Good Luck

remington 870 20 gauge express

My personal pick is Mossberg because I like the thumb safety(I shoot rifle & shotgun left handed so it much easier for me operate this style safety.) Mossbergs are also very dependable durable guns and normally are a little cheaper.

I can't say enough about fit. The gun has to come up easily with the cloths you wear hunting. I'm 6'0 tall, but have the stock cut down to 13 1/4 inches, a full one inch shorter(about) than the standard length stock.
You can not go by the old belief of putting the gun in the crotch of your arm, and measuring your index finger to the trigger. When mounting, the thumb on your right hand should be about 2" (rt.handers) from your nose...closer, and you will get smacked in the nose, and considerably longer you need the stock shortened. The stock should come to a spot under your cheek bone with your head erect (not bending over) and only having to shove the gun slightly out in front of you, not way out. You can then look in a mirror and see that your eye is just above the rib/barrel of the gun placing your eye properly to be the back sight...higher you will shoot high, and lower you shoot low... eye to the left you shoot left, and rt, you'll shoot rt.

realy what ever fits you best just stay away from the junky models. i would recomend looking around at gun shows or going to a skeet range and ask some of those guys what would be best.