I've made posters for a few events in the past. 

The Video Game Tournament poster (seen left) was for a club even at my high school. Players faced off playing a game called bushido blade. I used several elements from the game's cover such as the title and splattered lettering. I Limited myself to black white and red to give the poster a lot of "punch," it was a fighting game Afterall. I also the poster to have a bit of a feeling of motion so the white lettering is asymmetric and fellows like a diagonal blade slash.

The Drowsy chaperone was a Play held by my high school, and I was assigned the task of making the promotional posters. They wanted to do two runs of posters, the first (above and to the right) was made while we could finalize plans for the photoshoot that would be used in the second run (upper left). It was a new learning experience for me, as I needed to fit a lot of information about the location, price, and credits in accordance with the marketing requirements.