Keyboard 1: Quickly add symbols
You've probably been using your iPhone's keyboard for ages without realising that it's actually easier than you thought to add symbols to your messages.
Instead of tapping once on the 123 button, once on your chosen symbol and then once again on the ABC button to go back to the conventional keyboard layout, you can do the whole thing in one gesture.
Tap and hold the 123 button, slide your finger to select the symbol you want to insert, then release. Once it's been added, your keyboard will automatically revert back to the letters keyboard. One tap instead of three: that's some serious time savings right there.
Oh, and while we're talking symbols: hold your finger on the symbol for a second or two and you'll see any alternative (usually related) symbols that the button can offer instead. The dollar key also offers pound, euro and yen symbols, for example.
There are many additional symbols hidden within your keyboard that you may never have discovered. Experiment