First off, these strategies are just for playing against the computer. Playing against other humans is totally different and these tips won't work. . .
1. Develop long range superiority, especially for defense. The AI doesn't handle fighting against rocket launchers very well at all. Use LAV's to hold the front line and save up your revenue to buy rocket launchers, as many as you can. The AI wastes all his time and resources beating against your LAV's while you slowly pound his attackers with your rocket launchers.
2. When ready to invade a neutral country or enemy ally, invade first with LAV's only, I usually only invade with 1 LAV on the first turn. The enemy will have to raise guerillas, and then you will have a better idea of how to finish the attack. I try to have a couple of rocket launchers laying back in my country, and once the enemy discloses his guerillas, then pound them from afar with my rocket launchers. Once they are gone, then re-invade with whatever unit you want and take the capital. I've never seen the AI hold back from disclosing his allies, so you shouldn't have any surprises after your initial attack.
3. To defeat enemy rocket launchers, buy a transport, and load it up with a rocket launcher. Make sure it is out of range of the enemy of course. Then on your next turn, move your transport in, unload your rocket launcher, and fire - 1 hit will eliminate his RL. The same works for enemy death turrets also, but it will take 3 RL's to kill 1 death transport.
4. Just remember that unlike against human opponents, you don't have to be quick or mobile or try to surpise the AI. It's much more effective to be patient and slowly wear him down. Rocket Launchers are a great way to do this and are my favorite unit for fighting the AI.
5. Two LAV's are almost always more useful than a single tank, and they cost the same. Tanks have better mobility of course, but mobility is not necessary against the AI. Having many LAV's will slow you down, but it will also slow your enemy down, and if you are prepared for it (by having rocket launchers behind your line), you can slowly destroy his forces.
6. This tip is especially for scenario's, but also works a little in world wars: When the AI is invading, he often has a force of LAV's against his border and you have a force of LAV's against your border. A good strategy is to not kill his LAV's! Instead, use your long range Rocket Launchers (you may have to save up a couple revenue turns to afford them) to kill his stronger units behind his front line. Especially kill his morters and Ostrich units. That way, he can only attack with his smallfoots which can only do 1 damage each, while his more power units like tanks are stuck waiting to move, and you can safely pound them from long range with your rocket launchers. The only thing you have to worry about are his rocket launchers, but there is a way to prevent him from using his RL's. The AI won't bring his RL's into range of your RL's, so if you are able to position yours right behind your front line of LAV's, the AI won't risk shooting your LAV's with his rocket launchers for fear of you retaliating with your RL's. However, this requires that the AI not have any Ostrich or scorchers that could hit your RL's right behind your front line.
The first few times I faced the AI he wiped me clean, but once you start to figure out it's limitations, you can easily beat the computer every time. Hope these tips help out, and please, if you have any other suggestions post them here, I'd like to hear what you think. And feel free to criticize my strategy, I won't be offended. But just don't say how these strategy's won't work against other humans, because I already know they won't work the same way.