Here's the list:
1. Use Technology to Get Ahead
The benefit of having a Grand Theft Auto in the present instead of the '80s and '90s – new technology. Niko can keep in touch with his comrades by using his cell phone. Tap into the Internet and police computers to locate and identify targets and use the car's GPS system to get where you're going faster. Bonus for jacking nicer rides: they come with voice-enabled GPS systems.
Can you hear me now? Cell phones and other tech will play a big part in GTA IV.
2. Harder Police Alert System
Escaping the police gets trickier this time around. Once five-oh is on your tail, the search radius in your HUD gets wider and you have to escape. Get spotted by a cop while still inside the radius, the search area re-centers on you and you have to escape again. The good news: big shootouts during missions don't necessarily alert the police to your presence.
Expect a lot of this. The cops in Grand Theft Auto IV aren't as dumb as they look.
3. No More Character Customization
Rockstar removes the character customization and light leveling up (by eating, working out) that was included in San Andreas and returns the focus to the main character and his climb up the criminal ladder in Liberty City.
Not a fan of Niko's threads? Tough. GTA IV features no character customization at all.
4. Scale Tall Buildings
Since the game takes place in a big skyscraper-filled city, the action will go vertical this time around. Niko will embark on missions that involve riding to the top of a tall building to snipe at enemies below. He'll also be able to commandeer helicopters and land on top of buildings at times. Also, shooting enemies standing on tall buildings or platforms might, if you're lucky, send them into a spectacular dive onto the pavement below.
Find the perfect sniping sweet spot atop one of Liberty City's many high-rises.
5. Control Your Aim
You can aim freely, lock on to targets and all weapons include a zoom function (certain guns will zoom more than others). The weapon selection has been paired down from the ridiculous -- e.g. no more flamethrower, chainsaw – to the more standard rocket launcher, sniper rifles and automatic weapons like an AK-47 and M4 assault rifle.
Light fools up with style and grace the likes of which has never before been seen in a GTA game.
6. Hail a Cab
Instead of always jacking cars to get around, you can hail a cab and choose a destination by setting a waypoint on a map, or choosing from a list of predetermined locations. You can either sit and enjoy the scenery, or for an extra fee, press a button to skip the Sunday drive and arrive immediately.
Even the most bad-ass street hood isn't above taking a cab from point A to B.
7. Make Friends
Never underestimate the power of schmoozing, in real-life or in Grand Theft Auto IV. In-between missions, call up your cronies to hang out and build relationships that can lead to say... someone meeting you in an alley with a secret stash of guns. Or, meet your cousin at a bar and then try to drive him home safely after you're well beyond the legal limit (while the in-game camera sways wildly). Nothing builds the family bond like drunk driving.
Don't be a loner. Spend quality time with comrades for distraction and other fringe benefits.
8. Yes, There's Multiplayer
Grand Theft Auto IV will have multiplayer, which may include cooperative play in certain areas of the game. No other details have been revealed yet, other than it will involve more than "your standard deathmatch" shootfest.
Watch your back! Multiplayer means Liberty City could turn into a dog-eat-dog bloodbath at any second.
I got all of these from this website: