When I'm writing fiction, I'm not a profiler as C.S. Harris has discussed on her blog. I don't sit down and do a 100-question Q&A with my characters, though I'm not totally a seat-of-the-pantser either.
The Q&A is recommended in a lot of writing texts and may be useful for some, but when I tried it the answers came out goofy and didn't really help me define a character's voice.
I was working on a private eye character at the time and he wound up babbling about his need to help people. Having him articulate it didn't really define his drive nor did it keep him from getting locked away in three trunk novels.
Today in a limited way I do use a technique I picked up in a conference conducted by agent Donald Maas. I think the method is also discussed in his book Writing The Breakout Novel.
In the conference, he suggested jotting down major point-of- view characters and making note of the words they'd use for certain items. Simple things like pencil. If a character is a tech-saavy but harried executive might he say stylus in all instances instead of pencil or pen?
I don't remember if the Donald suggested an Excel spreadsheet but since I don't use pen and ink much that's how I do it.
Column A gets a list of main characters. Columns B,C, D and so on get some words as column headings.
I then try and determine what different characters would call different items. Everybody doesn't say "sofa" as Maas noted in that conference.
When you're writing a multi-viewpoint third person novel it helps make each character's narrative viewpoint more representative of that character's personality. I find it handy, and it helps with dialog too. Especially the column on the character's profanity of choice. (See Stewart and Cliff for more on that topic.)
It's fun finding different oaths and minced oaths. I once had a character who'd picked up some British slang which he'd use when he was angry: "God rot them," he'd spew.
Good luck with your characters.