The previous answers are right about looking at local newspapers as a an engagement announcement template. However if you're announcing it on mailed engagement invitations or online or any other way, there are some guidelines.
Introduce yourself and your fiance. Indicate your parents and fiance's parents. Often people include their education credentials and current jobs. Definitely include interesting or relevant information. People love to know what you're up to.
As for the wedding date, often people omit the specific wedding date in the engagement announcement. This can help so that no one knows you'll be out of the house (theft protection) and so that people who might want to come, but aren't invited, won't be able to easily crash the event. Just say a "fall wedding is planned" or something similar.
Source(s):
http://www.smartbrideblog.com