Here's a writing exercise/game I've played with writing students that can help prod the imagination and sharpen your characterization skills, as well as give you a little insight into your own assumptions.
Go to a random name generator site, like Kleimo's, and generate a short list of names. At Kleimo, you can pick males, females, or a mix of both, as well as an obscurity factor of 1 (most common) to 99 (completely obscure.) Here's one, a mix with an obscurity factor of 20:
Step 1: Write a line or two of story for each name. This can be a bit of dialogue, physical description, occupation, current life situation, or whatever the name itself suggests to you about the person who owns it. Just write down the first thing you think up:
Earnestine Trower kept her sensible shoes tightly laced, her white starched blouses buttoned up to her chin, and her hair so lacquered that it doubled as a safety helmet.
I suspected Clayton Gamet had been carousing out in our pasture at midnight again. Boy never seemed to sleep. But why had he spray-painted them red hearts on Pa's cows?
"Don't you love it?" Taylor spun around in a froth of pink tulle and black satin. "I bought it at Katy Raggs' boutique. Who'd have thought that dull little mouse could design something like this?"
I knew Mathew Nakasone was carrying at least five weapons and as many fake passports, but did I want to arrest him in the middle of his sister's wedding, or wait until he tried to slip out during the reception?
"Mummy, must we have Nannie Schrum to sit with us? She drinks all of Daddy's gin and then puts on his stripey pants and your hoop earrings and makes us sing pirate songs."
Step 2: Look over your name/story associations and see if you can recognize what made you make that particular association:
Earnestine sounds old-fashioned and unattractive, the combo of which makes me think uptight, rigid, controlled.
Every Clay I've ever known was a carouser and a fool for love.
Raggs to riches as well as rags in the expensive, useless objects that feed the vanity sense of the word; I don't like it when people call my daughter Katy.
Mathew's name triggered a strong image of a lean, dark, felonious multiracial cat burglar.
Nannie Schrum made me think of a bargain basement Mary Poppins and the -rum part of the name kicked in the alcoholic image.
Step 3: Now that you have a fair idea of the assumptions you make based on a name, take the same names, flip the character you created in the first step 360 degrees, and write another line or two of story:
You wouldn't know by looking at Earnestine Trower's bountiful, beautiful rack that she also came with a nice-size pool cue.
My Aunt Ruth claimed Old Man Gamet's Christian name was Clayton, but we kids were convinced that the nasty geezer had been born long before Christ, or maybe had even killed him.
The smallest cardboard box in Bender Alley belonged to Katy Raggs, judging by the three shopping carts of old clothes parked outside it.
"Cardinal Mathew Nakasone," I read from the candidate list. "Japanese-American, born in an internment camp, parents killed there, adopted and raised by Jesuits. Now he might make an interesting Pope."
"Come in, my pretty darlings," the elderly woman crooned as she beckoned from the door of the gingerbread house. "Old Nannie Schrum loves children to visit!"