how would you describe a character in a story to make them seem real but not to real

You want your character as realistic as possible anyway, it helps the reader identify with them.

Unless the whole point is to NOT identify them, like from a bizarre character in a comedy show, or a mysterious villain in a horror tale...for the first case, take the Janitor from Scrubs, and for the second, try the Odd Thomas series and pick up some hints.

Is the character imaginary? We need some more details.

If its an imaginary friend that you want people thinking might be real, keep the character fairly realistic. Nothing magical or extraordinary, but have them do things that aren't quite right, or a history that would only make sense to the child.
So a soldier would talk like a character from G.I Joe, the friend who shows up every once in a while says she's from the North Pole. Little things like that.

If you expand on what you want I might be able to help you more.

no I mean like not to over-exaggerated as to where people are going to read it and be like "aint no way this can really be a person"

Oh thats easy.

Use these links:
http://www.springhole.net/quizzes/marysue.htm Take this test with each character you create.
http://www.loony-archivist.com/ptcarchive/litmus.html Read this, its short and simple.
http://www.livejournal.com/tools/memories.bml?user=limyaael&keyword=Limyaael%27s+Fantasy+Rants&filter=all Read these entries. Best writing advice I ever heard. It covers practically everything you could possibly want to know.

the best way to learn how to do anything writing-related is to READ!... read lots of the best works by the best [not the most popular!] writers of what you want to write... study how they do it...

when you read enough, you absorb the 'how' and should be able to do it yourself in your own 'voice' eventually, without having to resort to following this or that person's 'how-to'...

Oh thats easy.

Use these links:
http://www.springhole.net/quizzes/marysue.htm Take this test with each character you create.
http://www.loony-archivist.com/ptcarchive/litmus.html Read this, its short and simple.
http://www.livejournal.com/tools/memories.bml?user=limyaael&keyword=Limyaael%27s+Fantasy+Rants&filter=all Read these entries. Best writing advice I ever heard. It covers practically everything you could possibly want to know.

thaks a lot I like the 1st one the best

Unless the whole point is to NOT identify them, like from a bizarre character in a comedy show, or a mysterious villain in a horror tale...

Interesting point. I'd never really thought of that.