If you haven't seen Iron Man 3 yet, and are awaiting the DVD release, beware the spoiler alerts below. And, more importantly, good job for not spending the money at the theater.
A lot of people liked it, based on its high rating on Rotten Tomatoes. Others didn't. While watching the movie (in the theater), it felt like I was looking at an Iron Man suit with nothing underneath--rife with plotting "don'ts" that all writers should avoid.
All good plotters know that an inciting event (the thing that puts the rest of the plot in motion) needs to happen within the first 25-50 pages of a novel (or first 15-20 minutes of a movie). Iron Man 3's inciting event happens all the way back in 1999, for reasons that aren't quite clear, other than a "scientific advancement" that could have just as easily been developed during the course of the movie. Instead, we have to believe that Tony was never contacted about it until 14 years after the fact. Uh. Yeah.
Inciting events that happen in flashback almost never work--and are difficult to do well. Avoid them, if possible, unless it's completely necessary to the story.
A plot more stranded than Tony is.
After landing in the middle of nowhere, Tony Stark meets a small boy who has no visible family (seriously--they never appear on camera). The kid is introduced with no plausible backstory, and then Tony just leaves him when he gets what he needs, including a watch and some other equipment. The watch is probably the most annoying thing of all. It's a Dora the Explorer stopwatch that the kid took (stole?) from his little sister, who also never appears on camera--all for the audience satisfaction of watching Tony Stark wear it on his wrist. Hilarious. A woman even stops Tony outside a bar and proceeds to ask about the pink, girly thing. In a twist, she's been tasked to kill him--but waits to jump him until he's had a full meal inside the bar.
Wait, what? Why didn't she just attack him on the sidewalk? Because the writers needed Tony to get some "necessary information" in the bar, information that could have easily been introduced beforehand.
The moral of this: be sure any plot elements you use are directly in line with the story and characters.
It's one thing to take your reader by surprise--and as writers, we're encouraged to. It's entirely another to build a really great premise for a villain--and then drop it completely. There was so much online vitriol about The Mandarin that the director had to publicly explain the decision--and not just for the purists. The precedent built in the preview was completely turned on its head for no apparent reason other than a few laughs.
Be sure your villain has as clear of a motivation as your protagonist. You can still surprise your audience--but don't disappoint them by not delivering on what was promised.
Seriously, Tony Stark is not this dumb.
Tony's house gets attacked because he discloses his home address on national television. I know he's cocky, but what would actually compel him to do that? Sure, it advances the plot and creates a really cool action scene where his house is ransacked. But Tony would know enough to keep his address a secret, wouldn't he?
If that weren't enough, it's revealed toward the end that Tony has a whole army of Iron Man suits in the basement that he could have pulled out at any time to save his house and protect Pepper. But instead, he waits to bring them out until the final battle, when they're completely unnecessary--so much so that he has to destroy them all.
Your protagonist has to have clear motivations for what he does--and they have to be consistent. If Tony Stark can do "Shakespeare in the Park" with Thor, he would definitely know to call out his army of Iron Man suits before his house falls into the ocean.
If you liked this movie, I sincerely apologize. But I see these same plotting mistakes addressed on author and agent blogs all the time--and I hate when they ruin franchises I like.