If you are looking to just "hang" it around your town on light poles or what not, FIRST check with your City Hall to see if it's legal.
Some cities, such as Burbank, CA, consider it littering and will fine you anywhere from $200 + a poster.
If you are going to hang them in local businesses (provided they say it's okay) then you should be fine with going to Kinko's or Staples and getting a colour print add done. You can design it at home to save money. I'd only do this if you're planning on printing a small supply.
If you are going to print in bulk, do black and white.
Your poster should have your promotional picture on it. I would recomend it be a high deffenition head shot. It doesn't have to be of you doing something, but it never hurts to have a pose that says "Magician". Usually levetating or burning something does that well.
Your title should be something short, sweety, and catchy. Expert Illusionist, or Magician For Hire! It should convey quickly who, and what you are, and what you do.
The title, and your contact number should be the largest print items on the poster.
Your poster should include your best acreditations, or testimonies. Such as "As seen at The Magic Castle."
Your Poster should be uniformed in colour. Headline and Contact Number should be one colour, body text and quotes, one colour. Your name, a third colour (if you want.)
No More Than Three Colours PERIOD!
No more than two fonts. Headline and contact number is one font, body text is another.
Don't do pull tabs, they are so cheap. It lacks class.
DON'T ADVERTISE A PRICE! Make them contact you for a quote.
NEVER GIVE A QUOTE! Always ask them for their budget. Ask that question 5 diffrent ways if need be.
IE: "How much did you pay the last magician?"
"Do you have a budget for this show?"
"How much did you plan on spending for your event's entertainment?"
"Have you ever booked a magician before?"
"If I quoted you at X.XX$ would that be too expensive for you?"
Also, always quote higher than you expect to get paid. That way you have room to flex without cutting your own throat.
Hope that helps.