I'd love to have seen what GameSpot would recommend in terms of multiplayer strategy, but I doubt that three months later it's ever going to be posted. :/
Your wish is granted. Our Twisted Metal Walkthrough provides tips for the 18 chapter storyline, tactics for online play, and means for gaining every unlockable.
Walkthrough: Sweet Tooth
Classic Death Match - Sunsprings, CA
Unlocks: SMG Sidearm
The very first stage is a Twisted Metal Staple: the Death Match. You simply need to destroy all of the enemies. This is the easiest stage in the game, so not many details can be given. You can use any combination of vehicles and be just as effective.
If you're low on health remember to use your garage to change vehicles. Also be mindful of the Health Semi Truck, as not only can it restore your own health, but enemy cars can use it as well. It's typically a good tactic to use the Semi even if you aren't badly damaged, simply to prevent the enemy from healing. Additionally, Sunsprings has at least four health packs scattered around town and many powerful weapons inside the movie theater.
Death Match - Killosseum
This stage is once again a typical Death Match without any sort of fancy rules, meaning the strategy is minimal. One thing to keep in mind is the very stage you're on. The Killosseum constantly changes its layout, revealing electric floors, structures with platforms, and different kinds of traps. However, this isn't the full Killosseum found in multiplayer and later matches, so it doesn't feature every hazard, such as the lava pit.
Because of the changing layout, consider using a vehicle with some kind of honing special , such as the Outlaw or Sweet Tooth. Still, any set of cars will be rather effective.
Electric Cage Match - Metro Square
Unlocks: Rear Freeze Ability
Finally, a match with some verity. The cage match still requires you to defeat all enemies, but you'll need to remain inside the green laser cage as much as possible. You'll start with a 150 second grace period which ticks down each time you're out of a cage. After the grace period is over you'll take constant damage when not inside a cage.
Because of this you'll want a car that has decent survivability and can still get to the next cage quickly. Death Warrant has the most balance for this job, but also consider Outlaw and Road Boat as backups. Yes, even though your goal is to get inside the cages, you can still head off track and switch cars in the garage. There is also a Semi driving around the stage, but going for it can be risky.
For the most part concentrate on a single enemy first--mainly weak enemies such as Kamikaze and Reaper--before moving into the thicker melee. Don't get too caught up in the fighting: always be ready to race to the next cage and preserve your grace period. You should turbo out of your current cage 3-5 seconds before it completely disappears.
Juggernaut DM - Watkyn's Harbor
Unlocks: Magnum Sidearm
You'll be facing off against the beefy Juggernaut. This enemy has a large amount of health (nearly 700), lots of firepower, and will spawn new enemies. This makes it priority number one. While the Juggernaut doesn't appear on radar, you can still see its name off in the distance.
You'll want a tough car for this match, namely the Outlaw. With a strong vehicle you can easily faceroll all over Juggernaut without much thought. Just remember to dodge the ball mines, as the splash damage is high enough to dent your defenses. If you do wind up close to the beast's weapons quickly put up your shield to avoid the brunt of the damage.
After Juggernaut is destroyed, it's now simple clean up of the remaining enemies. As always take out the low defense enemies, followed by the stronger ones.
Desert Twisted Race - Diablo Pass
Racing has a very different flow than any other match in Twisted Metal. You'll need to make it through the check point gates, arm the bomb gate, and loop back to the starting area. This doesn't mean you only need speed: this is still about destroying key enemies while taking the number one spot.
It's highly recommended that you pilot the speedy Kamikaze, as it's not only the second fastest vehicle but also has one of the best special weapons. The Kamikaze's secondary weapon will freeze anyone nearby, and can be charged to increase the freeze bomb's radius. This will be immensely useful for stalling the majority of the enemies.
Still a few cars, such as Crimson Fury and Reaper, will be a problem in a pure race. Instead of trying to beat these enemies with speed, destroy them with your heaviest weapons, namely ones that can quickly home in on the enemy or cause them to stall. Once these two enemies are dead, not many can compete with the sheer speed of Kamikaze. Just make sure to use tight turns liberally while be conservative with your Turbo boost; you wouldn't want to lose first place missing a turn or falling off a cliff.
The Brothers Grimm
You'll be up against two giant monster trucks that have lots of health and powerful weapons. There is no garage, but Sunsprings does have plenty of health packs scattered around. The recommended vehicle is one that can easily survive, namely Outlaw.
Always have some Turbo reserved to quickly escape the enemies or dodge their missiles. Pay close attention to the ground, as missiles can lodge into the ground and affectively become mines. The best strategy is to damage the Brothers as much as possible before retreating, healing up and rearming.
It's actually better to go after both enemies instead of focusing on one. By damaging both, you will have an easier time taking out the second brother later on. When the first enemy is destroyed, the remaining foe will armor themselves from all damage. Your goal now is to carefully drive between the monster truck's wheels and deploy your gunner.
Once this is done, wait for the next bar to fill to 100% and detonate your C4. This will kill your gunner, disabling access to your special but overall isn't much of a handicap. As long as you're already armed with main weapons and heeded the advice of already damaging both brothers, the armorless Grimm should die without a hitch.