It depends on your project! If you’re creating a black/white newspaper ad or printing for, say, Staples or FedEx-Kinkos, 150 dpi (dots per inch) will work fine. If you’re creating a four-color (CMYK) ad for a newspaper or magazine or sending your project to a professional print shop, your resolution should be set to 300 dpi. Let’s say you’re creating a very large vacancy graphic for your storefront; you may be able to use 72 – 96 dpi.
Before you start any design project, it’s best to interview several print shops in the area to make sure they can do the work you need. Once you decide on the printer, ask them what file format and resolution they need. The staff will be happy to help you get the answers you need.