1. For "What do little people want in clothing" Google brings you:
Now you know there are some businesses that are already catering to this market. Compare what's available with the demographics and psychographics you uncover to determine if your product will have a market.
Watch what words are being used, and by whom. What dos that population call themselves? Is there a medical term? Start a list of terms now.
2. Now that I have the basics, I can search for specifics: Little People organizations or little people statistics or little people attitudes.