Poster Design- Am I doin it right?

I need some help, guys. I agreed that I would design posters + flyers for a bar. But you know what? I generally design for web. Web sites? Easy, no problem. I can design you a sweet little pretty site without too much stress. But graphic design? This is a new fangled beast which I don't overly understand. I don't have any training in design, I figured out web design by trial and error. Yes this works, no it doesn't. And I have an okay eye, I think. I can tell when a site isn't as tight or as clean as it could be.

But poster design? *pulls face* I don't know what I'm looking at. I don't know how to achieve the look I'm going for. I don't understand why it feels wrong, why it doesn't look right. I don't know what I should be changing, what font weights I should be using. And I don't know how to do it better. Someone, please, tell me why it looks more like a book cover than a poster? Why my flyers are lopsided and wrong?

As you can see, I'm pretty much using texture to get me through. Texture is the way, apparently.

Anyway, what I need from you, dear internet, is critique. Tell me what I'm doing wrong, tell me what I'm doing right. Tell me what I can do better, and how to do it. Point me in the direction of graphic design/poster/flyer design principles site that tells me why I'm fucking up. Something that isn't or a site with a yellow clipart 90s design.

Help me be better, internet. What should I do?