Mission: First Flight
Hover and fly around target while firing your repulsors.
Mission: Fight Back
Destroy the turrets first and then put all your energy into the main target. While in battle - Every time Dreadnaught stops and becomes blue, avoid contact at all costs as this means it's firing an EMP (don't worry, you'll be fine). Make sure you have full armor for this one.
Mission: Weapons Transport
After Whiplash activates his shield, run around until he deactivates it. If you're close enough, hit him with your repulsors or punches (remember to re-rout all power to armor!).
Once he's hurt enough, Whiplash will hide up in the ceiling and a blue marker will become visible on the ground, indicating where he will attack, keep running around and this will be avoided.
Soon enough, he will come back down and repeat, just keep running. It would be wise if you had the Electro Punch upgrade.
Mission: Maggia Compound
While behind a pillar, wait for a statue to fire first then move to the next pillar. Soldiers will fire on and off from windows up above, use the gatling gun on them.
Re-rout power to weapons and focus on the three statues. Within a clear shot, use your Unibeam on one of the side statues but not the one in the middle (they need to be destroyed first). Just stay between their line of fire and any of the pillars and you'll get 'em easy.
A word of caution: Upon destroying each statue, a hole becomes visible in the wall behind it from which soldiers will start pouring through. Once again, the gatling gun is your best friend. Once the wave is over, finish the next statue until you reach the middle one.
Mission: Nuclear Winter
Similar to Dreadnaught. Run in circles when his shields are up to avoid fire and get away from him every time he stops with his shields still on. When his shields have lowered, hit with your repulsors or anything you got. All it takes is about 15 to 20 shots for him to go down.
A word of caution: Unlike with Dreadnaught, here you need to protect the nuclear containers while battling Titanium Man. He may use them for health regeneration, simply hit a few times and he'll stop.
Mission: Frozen Ship
This has to be the most annoying part of the whole Iron Man game. This guy is worse than the Riddler from Batman, it's all a mini-game here. First things first, know that the controls are running semi-backwards here (i.e. Left is Right, Right is Left, Up and Down are the same). The goal is to line up the two images on the screen with the right analog stick.
If you get it right all three times, he will compliment you and that's it.
Titanium Man (Part 2)
Mission: Home Front
Just like before, same strategy. Except the nuclear containers have been replaced with soldiers, tanks, and helicopters in the midst of a large battlefield.
The Melter/Bruno Horgan
Mission: Island Meltdown
Be careful here, Bruno doesn't take a break when it comes to using his weapons so Unibeam would be very unwise. All you have to do is be in a constant state of motion while using your repulsors and missiles (remember to charge them!).
Iron Monger/Obadiah Stane
Begin firing your repulsors from the get-go. Iron Monger has a lot of health, a machine gun, and a powerful missile launcher. Your Anti-Missile System comes in handy here.
Whenever he runs opposite the tanker, hover and dodge right away as he will begin throwing cars at you. It doesn't matter how many you destroy, he will keep throwing one after the other. Once he's done, give him two shots of your Unibeam (if you're on the tanker side across from him).
If you choose to punch him, he will pick you up and in this case, keep pressing circle so that he doesn't crush you. Charging up your missiles helps but doesn't do much damage though.
Once you've hurt him enough, Iron Monger will move on to a different area called Stark Tower. Avoid him until Pepper activates a switch - next, the center of the building will begin to glow. All you need to do is lead Iron Monger to this glowing area and he will sustain serious damage. Rinse and repeat two to three times and he's history.