At the top left of the screen you'll see a display that tells you what you should be doing. You can accept a new mission at any time; the reward for the mission (experience points) is also clearly spelled out, giving you an incentive. Three factors can influence which mission appears: requests from teammates on a special menu system; dynamic battle conditions within the map; and built-in events that happen as your progress through the map.
Which brings us to another point - each map is being built a bit more like a level from a single-player game; while they're still expansive and you're largely free to go where you want to, there will be an ultimate objective at the "end" of any given map - for example, a compound to infiltrate and destroy.
A variety of tools, vehicles and weaponry will, of course, be strewn across the battlefield. Shield generators which help the Strogg defense, for example, can be used or destroyed (depending on which side of the battle you find yourself on.) Air strikes are, of course, a possibility. In general, it seems that the developers are committed to putting in a full array of toys - and making the vehicles more drivable than in the Battlefield series, to boot.
So that's about it, by and large. There's a ton more detail in this game that's left to be seen - the quality of the graphics and gameplay is in line with the ideas we've been impressed with it. And don't forget to check out our video interview with the game's Lead Designer, Paul Wedgwood, while you're at it: