Enable character count
As Business Insider points out, every time you exceed 160 characters in a text message, your service provider charges you for another SMS. If you're on a limited SMS plan, you can keep track of your character count as you compose your messages.
Head to Settings > Messages > Character Count ON.
Use AutoText shortcuts to quickly type phrases
There are some phrases we use over and over again, like "On my way," "How's it going?" or even things like your e-mail address or signature.
To type these words and phrases faster, customize your own shortcuts. For example, typing "eml" would prompt your full e-mail address. Access the feature by going to Settings > General > Keyboard > Shortcuts.
Check out Rick Broida's very useful post, Ten handy AutoText shortcuts you should create.
Get the hidden Emoji keyboard
Once upon a time, you had to go through a set of complicated steps to get emoticons like smilies, hearts, and other clip art symbols on your iPhone. Now, the feature is built in to iOS 5 and can be enabled in a few steps. Check out the guide here.
However, know this: only fellow iPhone, iPad, and iPod Touch users will be able to see the emoticons. Everyone else will see garbled symbols, so beware of using emoji in fields like Twitter or Facebook status updates.
Skip Siri, but use speech-to-text
In my experience, it is not easy to go through the entire process of sending a text message via Siri. It's frustrating, time-consuming, and has a (non-scientific) 50 percent failure rate. (To be fair, you can make Siri more efficient with some configurations.)
A more useful feature is speech-to-text within the Messages app. So, you do the work of selecting the recipient, but instead of typing your message, you speak it.
Go to a message thread and tap the text field. Then tap the microphone icon by the spacebar, wait a beat, and begin speaking your message.
Turn off preview and badge notifications
There's little as heart-stopping as an awkward text message popping up onscreen for your nearby friend to see. The badge alert also happens to be annoying when you're in the middle of another task.
To fix this, you'll need tweak two things: message preview settings and notification type. Head to Settings > Notifications > Messages. Turn Notification Center ON, Alert Style: Banners, and Show Preview OFF.