I've shot a shotgun before but im not too good on gun knowledge. Im gonna start duck hunting this season and need advice on a good beginners 12 gauge shotgun. Is it easier to shoot and kill ducks with a pump or semi-automatic? What size chamber do you recommend? Brand? Any advice would help....Thanks guys!

To me, it's easier to shoot a semi than a pump. A good entry semi would be a Baikal MP-153. It has a 3.5" chamber, although you would probably be fine with 3" shells. I've been shooting a Super Black Eagle at ducks for the last 15 years, but I still recommend the MP-153 to people that want a shotgun. I know of 4 people who have bought one because of my recommendation. It's not too expensive either. 26" barrel is the most popular.

As far as shells go, I normally go through a case or two of Federal 3.5" blue box steel. Last year I got a reloader and have been pushing loads in excess of 1700 fps.

I'll never shoot a pump at ducks again. That being said they definitely are tried and true. If you go the pump route take a look at the Remington 870. Semi-auto there's a lot of good options out there but my last two have been Stoeger M2000s. Go with a longer barrel, it helps swinging it and also keeps it safer in the blind/pit. I see no need for 3.5" shells, but some guys swear by them. 3" have always worked out great for me.

It's easiest to shoot either; if the gun "fits" you well.

Welcome to waterfowl hunting. If, as you say, you are new to shotguns and waterfowling I'd be inclined to do the following.
I'd look for a good used 12 Ga. shotgun with a 28" barrel with either a fixed modified choke or choke tubes. A 3" chamber will more than suffice your needs. I'd also start with a pump shotgun. There is alot of excitement hunting waterfowl. Untill you've experienced all the adrenalin rush, a semiauto will just keep firing after each trigger pull. Not always a good thing when one is really excited, especially when hunting with a group. Best to start out, in my opinion, with something less automatic. As time goes on, I'm sure others you hunt with will let you try out there shotguns. After gaining alot of experience and confidence, you will have better knowledge of what you need and want out of a shotgun. Spent some time and ammo getting to know your choice of shotguns. Good luck to you.

I would recommend a Baikal MP153. It's 3.5" semi automatic w/ four extended tubes. It isn't exactly heavy so you wouldn't feel so tired carrying it while hunting. I got one and I find it a reliable partner for duck hunting.

my friend's dad just sold me a brand new Beretta 390 semi-auto. Any takes on this gun?

I shoot semi for duck and geese. I have used a pump when I started out.. I would recommend a semi like winchester or browning. I shot a 10 ga for late season and 12 for early and a backup for late

I shoot a pump or a double barrel.

My pump is an 870 with the 3.5" chamber, bought right from Wal-Mart,
My son shoots my Mossberg 835 pump action with the 3.5" chamber

My double is a Blackpowder double

Im gonna start duck hunting this season and need advice on a good beginners 12 gauge shotgun.