Promoting your concert can be an expensive process, so you have to make sure the advertising costs don't exceed the money your gig generates!
Here are some of the potential drains to your pocket, so you can prepare for the planning and budgeting of your concert:
1) Posters/ flyering
You may want to hire someone to design your posters and flyers for you, to ensure they have maximum impact on your target audience. Then there's the printing costs, and if you have money to spare you could even hire leafleters to help you spread the word as far as possible...
2) Ads in the press
This is where things could get out of hand. Try to keep your spending on advertising in alignment with the estimated scale of your concert, and the money you expect to generate from it. If you really think your gig could be huge, then go ahead and splash out with an expensive advertisement. Otherwise, a few ads in small, regional papers should do the job, and your local paper might even have a free advertisement section for events happening in the area.