There are many books, websites and articles that explain clear speech (i.e. plain language). Here are just a few of them:
Clear Communication: Part 1 – provides a list of tips to follow.
Document Checklist for Web Documents – includes a checklist for checking whether your document meets plain language standards (from organization, Plain Language.gov – United States). The site also includes a list of quick tips. www.plainlanguage.gov/howto/quickreference/index.cfm
National Adult Literacy Database (NALD) – offers information on clear communication in Canada, including information on training service providers and resources. www.nald.ca
Pennsylvania State World Campus – suggests tips for people participating in online forums or bulletin boards (13 Tips for Working Effectively with your Peers and Faculty). www.worldcampus.psu.edu
Plain Language Network (Toronto) – includes many tools and resources; includes plain language for legal documents. www.plainlanguagenetwork.org
The PlainTrain – offers an online tutorial, in both English and French, on plain language communication skills. www.web.net/~plain/PlainTrain
Word Dog – offers a trial software tool that will edit a business letter or memo, and indicate possible clear communication alternatives. www.worddog.com