If you choose to create your poster as a single large-format document, here are a couple of options for printing:
Poster Design and Presentation Tips
If you're designing a poster for a conference, read the sponsoring organization's guidelines and/or specifications carefully.
If you're designing a poster for a class, check with your professor regarding expectations for poster design. S/he may be able to refer to you models or best practices for poster design in the relevant subject area.
Design Better With CRAP: discusses the importance of contrast, repetition, alignment, and proximity in creating a strong, easy-to-interpret design.