Ask friends or strangers online to interview you and give feedback. I do this a lot with my team and do mock interviews. I want my team to promote and make more money. Maybe you can ask your boss for a mock interview and show them a position you are interested in. Lot's of resources to leverage. Hell I bet a lot of people here would help you out.

My piece of advice is to remember your star format, and if you don't know exactly how to do something. Tell them, and then walk them through how you would do it based on what you know. tldr; throw a hashmap at it.