Techrepublic.com published an article on using Mail and iMessage in IOS8 that you might find useful.
THe tips covered include
- how to write multiple emails at once [handy if you are in the middle of an email and need to refer to something that was previously sent],
- How to set what happens when you swipe left or right [you can swipe to flag, trash, or even archive messages]
- plus some tips regarding iMessage – how to leave a group discussion, etc.