Here is a very quick tip, probably something that you already know, but if not then now you do: the way to redial a number on the iPhone. This was one of the dozens of tips that Ben Stevens and I discussed last month during our ABA TECHSHOW presentation. There are two ways to redial in the Phone app.
First, you can tap the Recents tab at the bottom. This will show you all of the people who you have recently called or who have recently called you. Just tap a name to call.
Second, you can redial from the keypad. You won't see a redial button on the screen, but if you don't type any number at all and just hit the Call button, the iPhone will present you with the last number that you dialed. Tap the Call button a second time and the iPhone will redial that number. Thus, two taps of the Call button get you a quick redial of the last number that you called.