Writing in third person is projection. You project your opinions, ideals and hopes onto the character, then you give different ones to another so they suit their role in the story. There's no need in fact to have a proper introduction. Stories that start with for example: Sue was a teenage girl of average height and brown hair, with green eyes. She has good grades but not many friends at school etc... are blatantly boring in general. If you know everything there is to know about the character, then there's nothing more to find out.
Some writers will write out of character information ALL the time. Their descriptions are focused entirely on how an audience views the characters (lots of description about the characters' appearance, the colour of their eyes, the perfection of their skin etc, when there's absolutely no need for it). If a character starts the story at a point where he/she is running for their lives, what the reader wants to feel is the excitement, the pounding of their heart, the pain as they try to draw in breath, their side aching from the sprint, and maybe the drag of wind and branches in their brown hair. You can fit descriptions (introduction) into a piece of writing without ramming it down a reader's throat.
People are much more interested in the story than the appearance, it adds to it certainly to have a solid image of their character, but that doesn't have to come right at the start. Readers can find out someone is at school by you talking about them going to school, or getting a call from school friends, or doing homework. They can find out she's a girl because you keep referring to her as 'her, she', and they can find out about her appearance in bits rather than a single large chunk (she might wash her hair and you can note her dissatisfaction with its brown colour, you could talk about her putting on make up and choosing a shade to suit her green eyes.
There are elegant ways to introduce characters, they don't all need to come into a single paragraph. Good authors make characters (especially the main one) last. It can take half a book for a reader to know most of a character's personality and habits, then it starts to change as the story progresses. Always leaving the audience curious and wanting that bit more information is actually a useful tactic in writing an engaging story.
It was too easy to figure out Twilight's events because you just had to think: Insert more pretty words, make sure all the pretty people are focal, and make sure all the focal people are pretty. Make up enemies that make the heros look as good as possible, then insert already perfectly described heros into said situations. Since we already know that the heros are: perfect, then it's really too easy to see that the good/perfect will triumph over the evil/ugly. Keep audiences guessing to write a good story, write wish fulfilment (everything you want/expect to happen happens) if you just want readers to flock back for the feel good value (everything they wanted/expected happened).