I've found something that really helps me see my characters better, but first, the conundrum.
When I'm making a new character, I write down dominant physical characteristics. I fill out personality worksheets. I do character interviews, surveys, and yet more worksheets. Even after all of that, when I picture my characters in my head, I don't see them very clearly. I can see their surroundings with ease, even down to the litter in the gutter, but the characters are blurry watercolor people drifting through a backdrop of photo realism... I know what they'll do, think, and say, because I KNOW them but I can't make up a randomized appearance in my imagination.
So, I don't want to base my characters physically on people that I know because I would be irate if those people's personalities started to show up in my characters. So if I can't make them up, and I can't use the physical characteristics of real people. That leaves me with... actors.
And it's helping. Every scene seems far more intense now that I can really SEE my characters moving around my settings. It also gave me a fun project. Scissors, tape, markers, and I now have a little notebook with character bios and pictures.
So what do you see most easily? Is there something for you that's hard to see? Does anyone else use actors as character models?