How have your experiences selling baby gear been? Do you have tips or tricks?

I feel like I'm doing it badly! I've been posting things lo2 grows out of on local Facebook boards and mostly get crickets. Or someone will say they're interested and then disappear. I also never know how much to ask for things! I list it as "best offer" and then they just ask me how much I want, I say something like 50% off the original price, and then they disappear rather than negotiate. What am I doing wrong, lol??