Determine what event you'd like to design a poster for. This could be for a concert, performance, lecture, etc. We recommend choosing a real event so you can research your subject and deal with real world considerations.
I've always loved the Black Angels. Their sound and presence is such classically kickass rock'n'roll. They're hitting the road again in April to support their latest album, Indigo Meadow, and coming to San Francisco's The Fillmore on May 17, 2013. I feel that that show is perfect, considering the important role that The Fillmore has played in psychedelic art.
Here's a taste of art they've used in the past.
2. Research Part II
Once you've settled on a subject, dive a little deeper to understand who they are. How do they represent themselves visually? If they're a band, what do they sound like? What messages or themes are important to them? Wikipedia is a good place to start but you can also look for more personal interviews and articles that will give you additional insight.
Their throwback psychedelic style - both in their music and branding - is instantly recognizeable. The spun out, repetitive linework reflects their heavy, patterned beats while the contrasting (even vibrating) colors are a nod to psychedelic art pioneers like Stanley Mouse and Alton Kelley.