Find a list of contact details for plotter suppliers in your area. Browse through graphic design magazines or newspapers for advertisements. Visit directory websites such as Kellysearch.com or Industry Mart for supplier contact details (see Resources).
Decide whether you are looking for a new or refurbished plotter. A refurbished plotter is a lot cheaper and delivers the same quality work. A new plotter, on the other hand, comes with a factory warranty and sometimes a service plan.
Pick a plotter width. Most models come with either 24-inch or 36-inch carriages. The smaller 24-inch plotters are usually cheaper than the 36-inch models. If your posters are not going to exceed a width of 24 inches, opt for the smaller models.
Focus on either a roll feed or sheet feed plotter. Roll feed will allow you to print posters of virtually any length, but requires cutting the paper when a printout is completed. Sheet feed models load sheets of a predetermined size. Roll feed models might be a bit more expensive since these plotters usually have built-in cutters.
Take your high-resolution, full-color digital image on a USB stick or CD to several suppliers and ask for a test print on the model of plotter you are considering. Ask for a glossy or semi-glossy print if you are planning to print your posters on this type of paper.
Ask each supplier for additional information on the model plotter you are looking at, such as price, print speed, ink cost, warranty and a service plan.
Compare the color, brightness and print quality on the printouts from the different models. Use your magnifying glass to compare the grain (dither) of the printouts. Decide which color-hue you prefer, as printers all interpret colors slightly differently.
Purchase the plotter that meets all your requirements and suits your budget.