I get stares. Blank ones. A lot.
Because I've chosen the wrong word. A word that, while it is understood (kinda), is simply not used in conversation. It's a written word. Or an old-fashioned expression. Or a technical jargon (専門用語）.
Couple this with a pronunciation that is...not quite perfect...and you get stares. You do.
Breaking this down, I've found that this is do to the sheer number of words in Japanese. You have your technical jargon, idioms, 書き言葉 and 話し言葉 -- and then, as a learner, you have to wade through these to determine which are used at what time. It can be an arduous task, to say the least.
And to be honest, I have yet to figure out a way to conquer this problem. I suppose it's just trial and error. Listening and repeating. But I have no idea.