Game Informer Magazine's next issue contains a lot of new information regarding Mass Effect 3. Some info may be spoilers so you have been warned but i'm sure people interested have played Mass Effect 1 and 2.
Mass Effect 3 starts with Shepard on Earth. He is on a trial in regard to the events of the Arrival DLC. During the trial, the Reapers attack earth and the prologue involves Shepard escaping to the Normandy to find allies who is currently battling Reaper soldiers.
Squad mates that are confirmed to return are Liara, Ashley/Kaiden, Garrus and James Sanders. Of course, this all depends on your save. So if you want say... Garrus to be on your Mass Effect 3 game don't let him die during Mass Effect 2. James Sanders is still unknown but we do know that this isn't the guy in the teaser trailer. Who is he? have no idea but Jason Statham should voice him.
There are other old squad mates from previous games returning but are not playable. Wrex, Mordin, Legion will return but won't be playable characters. Anderson will also appear in Mass Effect 3.
Mass Effect 3 will have a "previously on Mass Effect" similar to Mass Effect 2's interactive comic for the PS3. It sets up your story if your playing the game from scratch. Which is a good idea but i highly suggest you get your saves ready because the fact that your choices matter since ME1 will make a difference.
The Illusive Man is back but with a more prominent role this time around. Cerebrus is still around but is now hell-bent to kill their 2 Billion investment(which is Shepard). why do they want Shepard dead is still unknown but i have a feeling it has something to do with the choice you'll have to make in the end of Mass Effect 2.
More RPG elements will be added in Mass Effect 3. It won't be as much as Mass Effect 1 but will definitely be more than Mass Effect 2. More freedom will be given in character progression with bigger skill trees and abilities that can evolve more than once.
Weapons will be Mass Effect 2 style with a set list. Since their adding more RPG elements to the 3rd, they will be returning the weapon mods concept from ME1. You will have the option to change certain parts such as barrels, scopes, and so on to improve the weapon's performance and appearance.
All classes can now use all weapon types, but only the Soldier Class can carry all weapon types at the same time. Other classes will have a limited number of slots. It's ok though. For example, you pick the infiltrator class(sniper class), you can at least replace your pistol and use assault rifles together with a sniper rifle.
Mass Effect 3 will have numerous endings. They will have some good endings, some bad but who you have in your squad and which allies you recruit can have a drastic effect on which are available.
There's more we want to know about this game! but at least were finally getting something. Everything mentioned is again on the latest issue of Game Informer and if you have access to that issue enjoy. Hopefully everything mention will stick until the game ships because everything sounds awesome. Can't wait for more info about the last chapter of the Mass Effect series.
Mass Effect 3 has no release date yet but is set to be release at the end of this year on PC, Xbox 360 and Playstation 3.