I am not one of those writers whose characters talk to them, not in the literal hearing-voices-in-your-head way, nor do I like using that as a metaphor for character creation. Probably because I like to be in control. I also think that's why I never got into role-playing games; I didn't want other people's ideas interfering with my own and changing them. I talk to other people about my characters sometimes, and have used ideas others have given me, but I don't think that's the same; I'm still in charge of my own characters. But enough about me wearing a crown and being The Mighty Dictator.
What techniques do I use? The below methods are useful mainly, I think, for novel characters more than for short stories.
Umm, well, not really brilliant, but you clicked, didn't you?
Things I do to make characters, in no particular order:
1. Give character a name and gender. This in itself often tells me other things; for example, to pick a name I might have to know the character's ethnicity.
2. Figure out the character's function in the story. Sometimes, often, this comes before name and gender.
3. I don't write the biography of my character. I usually make things up as I need them, or as they occur to me. A current novel character is the sidekick in the previous novel. I knew he had a lot of sisters, and in the previous novel, I showed a couple of them and named one other. Now that he's the star of his own novel, I had to name all of the other sisters, and name their husbands, and figure out how many children they had, and what their problems were that would make the star's life problematic.
4. Stuckness from not knowing character well enough: sometimes I make notes. I've tried the "list of adjectives to describe X" technique with some success. Also, "what are X's problems, and what in his character made these problems terrible to him?" To figure out the various sisters in #3, I made notes on one sister at a time, decided on a problem for her, and in the process figured out some of how they related to each other as well as to their brother. A cheat I've used a couple of times as a starting point (not this time, but before) was to use the characteristics of a particular Zodiac sign, taking the descriptions from an old baby name book I have.
5. Stuckness resulting from a pile of notes that haven't coalesced: I write scenes with the character included. Dialogue is most fun and works well for me, and is most likely to produce revelations. Arguments are good. Losing control is good. What is he or she like then? I don't think a writer can really understand a character until they've written her into scenes. Anyone can make a tipsheet. It's showing the character in action that makes her live.