The purely technical content below is likely all in the iPod touch User Guide, a link to which is initially provided in iPod Safari. Apple has apparently replaced the previous iOS 4.2 PDF file with one for iOS 4.3, and another for iOS 5.1 is available (as of 8/25/12, anyway).
See Settings > General > Keyboard for some of the following. I changed some of my settings, and no longer remember exactly which ones were the factory defaults. Experience-based comments below are mine. I use many of these techniques frequently.
- When editing text, to bring up the choice of Select / Select All / Paste, two quick taps after the end of the line, before the next line (if applicable), is faster than tap-hold; if you're in the search bar, there is no next line. If you are replying to an e-mail message, two quick taps before the body text of the e-mail to which you are replying may do the trick (it did for me in Yahoo! mail). Cut or copied text survives even turning the iPod off (by holding the button down for several seconds and doing a slide to power off); if you've never cut or copied text, presumably Paste is not an option.
- Double-tap on a word to bring up Cut / Copy / Paste / Replace. Replace will offer suggestions if it can.
- To select the text from the left margin (after a hard return, if you are not at the top of the file) until the next hard return, use two fingers simultaneously, with space between them, to tap the text. Not easy to do on a short line of text, where the alternate, equivalent-effect technique of rapid quadruple-tap should work better. Quadruple-tap is also helpful if you have only one finger to spare for such text selection, e.g., if you are holding the iPod with one hand and even using a finger from the same hand to do various actions.
- If you have Auto-Capitalization enabled in Settings > General > Keyboard, the pronoun I and some words like English can be entered lower case; iOS will capitalize them.
- After existing text, tap space twice to get a period and a space. It's common to want a period and a space. You can of course then delete the space, if it's extraneous. This technique is efficient for things like "p." (page). It works perfectly for things like "St. John" because the first letter after the period is capitalized, so you could just type S-t-space-space-j-o-h-n, i.e., you don't have to tap Shift to get a capital J.
- Many contractions such as can't and won't can be typed without entering the apostrophe; iOS will put the apostrophe in.
- If you want to undo the typing (pasting) you've just done, shake the iPod. You'll be given the choice to Undo Typing (Undo Paste) or Cancel. If you choose the Undo X option, shake the iPod again to additionally get a Redo Typing (Redo Paste) option, and be presented with another level of Undo. Not sure how many levels you can get. An interesting practical difference between the iPod and iPad; here's a thread on shake/undo for the iPad. Not every operation is easier on the iPad!
- Analogous to the previous tip, Undo Delete is also possible with a shake. I usually need this when I am editing a longer piece of text in an input box (like Title for a Calendar event or Safari's search bar), and my finger comes close to the X delete-circle-icon, and I accidentally touch it, inadvertently deleting my text.
- I previously wrote about getting Special characters in French and Spanish, and I just learned from http://www.tcgeeks.com/30-essential-ipad-tips/ that the analogous technique applies to getting a web address suffix different from the .com, like .net or .org. Presumably it's because I have a traditional Chinese keyboard enabled that I can also get .台灣 (.Taiwan).
- When using either the letter or number keyboard, you can get a single character from the other keyboard by tapping and holding the "123" or "ABC" key (whichever is available), then drag your finger to the desired character, finally lifting your finger from the screen. After that, you will return to the keyboard from which you started. (This behavior is not applicable to the "#+=" keyboard which is accessible from the number keyboard.) This can be useful for things like "e.g." and website names (aaa.bbb.ccc).
This technique saves typing for text with intermixed letters and numbers (and/or punctuation, like the "h-j-k-l" I needed to write a couple of times). Punctuation using a matched pair of characters, e.g., parentheses, single quotes, and double quotes, can be much more efficiently entered. Chess writers like myself will find this technique (and the next one) beneficial for typing game moves such as "1 e4 e5 2 Nf3 f6?? 3 Nxe5!".
- When using the letter keyboard, you can capitalize a letter which wouldn't otherwise be capitalized (e.g., the a in apple if you wanted to refer to the company) by tapping and holding the "shift" (up arrow) key, then dragging your finger to the desired character, finally lifting your finger from the screen. This may be faster than tapping shift, then tapping the letter.