Be true to the material, but don't feel handcuffed by it. Know when to push the boundaries. Research the comic, sure. If possible, talk to the creator of the book & get his/her input. Or talk to some of the more recent writers & get their take. But remember that ultimately this is
your movie. You are the one the fans are going to hold accountable. Don't be afraid to think outside the box. SOmetimes it pays off.
Don't let whiny, nitpicky internet fanboys push you around. Many of them don't know what they want. Many just like to complain & will go online to trash your movie no matter how many things you do right. Comic fans are notoriously resistant to change & now have the perfect medium in which to vent. Many of them have the movie written, directd, cast & shot in their heads & will reject anything that deviates from this. Many will complain about even the slightest change, & many will praise & uplift one movie that takes numerous liberties from the source material while trashing another which takes the same amount. You will not please all of them & there's no point in trying. These people complained about organic webbing, leather uniforms & rubber armor, while pouring tons & tons of money into the very movies that they criticized.
Cast based on suitability to the role, not looks,
success in other genres
or popularity with the opposite sex.
Even though some of the choices may prove controversial, if the person gives a top-knotch performance,
the fans will come around. Remember this above all; Ask yourself-can you sell the movie without putting their name on the poster?
Focus on the movie you're making, not on the sequel or spinoff you
hope to make later. It's fine to set the stage, but don't make a throwaway movie, just to get it over with.
Selling toys, lunchboxes, etc is not your job. Make the movie. Let the studio worry about that other stuff. No amount of merchandising is worth a 2-hour commercial that's all fluff & no story.
Remember that you want to appeal to more than just kids and/or hormonal teenagers.
Know when to get out of the movie's way. It shouldn't be more about you than the character.