Painting a complete picture of your characters not only helps you get to know them better, but it's also ridiculously fun. (Especially when you're a mom with three jobs and you're painting a picture of your protagonist's chiseled love interest... but I digress.) It's also really easy.
The old fashioned way: grab a few magazines and cut out any and every thing that makes you think your characters: clothing, colors, faces, bodies, personalities, accessories, locations, etc. Separate them into piles per-character and then glue/tape them to an "inspiration" poster board. Write notes on your board as they pop into your head: catch phrases your character might use, bits of dialogue, memories, plot ideas, whatever strikes your fancy. Write it ALL down. You never know what little gem may tumble from your brain as you cut away like an 8 year old in art class.
The www. way: Pintrest. It's amazing, addictive, and a mess-free way to create inspiration boards for your characters. With a couple of clicks, you can pick an image and put in on a board for your character, and then keep on perusing. I usually run out of time before I run out of attention for Pintrest. I have even started inspiration boards for a couple of my main settings as well. Warning: I'm a homebody, and the pictures on pintrest of amazing sights all over this world have made me want to travel. Bad. (site url: http://www.pintrest.com)
An added bonus to creating online inspiration boards: your fans and potential readers can see exactly what was going on in your brain when you crafted your character/setting. And any link between a reader and a character only serves to strengthen the bond between them. For those of us penning a series, this is particularly helpful. I want my readers to KNOW my characters. I want them to have feelings for them: love, hate, fury, etc. And it's a lot easier to feel those things if you have a high-resolution picture in your head.
Just for fun, I'll post a few pictures from the inspiration boards for my main characters here. I think the old adage: a picture is worth a thousand words rings true. How many words will your inspiration boards create in you?
Here's a link to my pintrest page: http://www.pintrest.com/jadiejones1. I've created inspiration boards for my main characters and a couple of settings. If anyone has any other websites or ideas on this topic feel free to post - and please include and blog/site address.