Like nevalnin said, Fallout Tactics is much more about tactical combat than it is storytelling, although there are are a smattering of mini-quests and intermission briefings which give updates to what's going on in the world while you're saving it.

Continuous Turn-Based (CTB): This is what FT calls real-time combat. You have a certain number of action points, which all actions use, and regenerate at a rate based on your agility skill and certain perks or traits you may have allocated to your character. All players perform actions simultaneously during CTB, including enemies. You can alter your players' disposition to three levels of awareness: Hold your fire, Fire if fired upon, and Fire at will. Unless you are performing stealth, Fire at will is your best bet, if you're using CTB at all. Some players prefer the old standard turn based way, but I've found it gives the game dreadfully slow pacing, and most missions are not so hazardous that you need the precision that turn-based gives you.

Energy Weapons: Like Fallout 1 and 2, you eventually graduate from conventional weaponry like pistols, automatic rifles, and even miniguns to plasma pistols and rifles. These are extremely important because you'll be fighting humanoid robots (and worse stuff), and they have an automatic 50% damage resistance. Whereas before you may have done over 200 points damage to a raider with your massive Vindicator minigun, you may only do 5 or 6 points to a robot. This is bad. I waited too long to start investing my skill points in Energy Weapons; don't make the same mistake. You WILL need them.

Miniguns: Miniguns, like the Avenger and its big brother, the Vindicator (TWO of which you can nab from a special encounter involving two Brotherhood of Steel guards if you're lucky enough to find them), are, IMO, even more useful than they were in Fallout 1 and 2. There are more players available with the Big Guns skill, ammo for them is relatively plentiful, and they're tremendously effective--especially at close range. A great tactic: if an enemy is crouching behind a sandbag wall, approach him with your minigunner while crawling, and then stand up once you reach the wall. A point blank blast from a minigun will annihilate most opponents.