1. If you find the iPhone keeps trying to correct a word you often use you can train it, contrary to what you may have heard from some reviewers.
From the PDF manual:
To reject the correction, finish typing the word as you want it, then tap the word before continuing to type anything else. (The second time you type the same word and reject the correction this way, iPhone adds the word to its dictionary.)
2. It is not a good idea to wipe the screen with the phone on due to the possibility of generating static electricity.
The manual recommends you turn it off and disconnect it before wiping the screen. (That's what that nice little micro-fiber cloth is for.)
Both of these tips were discussed in Podcast 81