Interesting character quirks are responsible for some of the most memorable characters in fiction, but I think new writers sometimes forget that a quirk doesn’t make a character. It’s a good place to start though! The first page of this worksheet gives you some questions to develop character from quirk. If your answers are thorough, you might even find the seeds for plot, setting and supporting characters.
The second page is my favourite, though there isn’t much to it. I recommend sticking it to the back page of your writing journal, to keep a list of character quirks you come across in real life. I’m sure that after a brief mental survey of your friends and family and some surreptitious people-watching, you’ll easily fill the whole sheet!