Congratulatory Messages

So I am trying to write a congratulatory message and what does one say? Should I send it right away or is it better to wait a few days? Of course there should be compliments and definitely no bad news or negative comments. There are many different theories, but for some great advice I am headed to www.writeexpress.com for some great tips.
Copyright © 2014 Dictionary.com, LLC. All rights reserved.