I made a poster for my sister last year, and I may have put a little too much work into it. What I have below is what it ended up looking like, but I started with some much more complex ideas.
For a poster, you don't want complex. You want to convey you message in the simplest way possible so people want to actually look at the information provided.
So it took some revising to get this one straight.
And the more things I removed, the better the piece looked.
I loved how it turned out, and even though it was only for an event at a University, I think it was good practice in design.