Autocorrect is a boon from the computer gods for anyone engaged in tiny-screen typing, but it's also the bane of every iPhone and iPad user's existence. You can accept the gift and avoid the grief by paying attention to a few details.
Mistype a word--or even start typing a word properly--and autocorrect charges into the fray, offering a helpful suggestion to correct the misspelling or to save you the bother of completing the word letter by letter. And there's the first potential problem: If you've actually finished an unrecognized but correctly spelled word and you type a space or a punctuation mark, or tap Return, autocorrect will infer that you've accepted the substitution it recommended.
According to Apple's instructions, the way to dismiss an autocorrect bubble is to tap the tiny X inside the bubble. Fortunately, you don't have to be that precise: Tap anywhere in the bubble to reject it.
That's not much help on an iPad when the bubble happens to be far from the keyboard. Fortunately, you can overrule an autocorrect suggestion from the keyboard: Tap the Delete key, retype the last letter, and the suggestion disappears.
When you override an autocorrect suggestion, iOS learns your preferred word. Earlier iOS versions learned more slowly, requiring you to issue vetoes on several occasions, but iOS 6 often learns from a single incident. The program then stores your words in the inaccessible, noneditable Keyboard Dictionary. Once a word is in there, autocorrect will not attempt to correct it--and will even suggest it as a correction or completion. That sounds good, but it can be a problem.
Suppose that you type tge and you're so used to dismissing autocorrect that you precipitately reject its suggestion of the. Now every time you type tge, you must manually correct it.
There is a workaround, however: You can trick iOS into thinking that tge is just a shortcut for the. Go to Settings > General > Keyboard; scroll down if necessary, and tap Add New Shortcut. Type the in the Phrase field and tge in the Shortcut field, and tap Save. Henceforth, if you mistakenly type tge, iOS will correct the spelling to the.
If you have accumulate lots of mistaken entries in your Dictionary, you can adopt the nuclear option and erase all of the words your device has learned, en masse: Go to Settings > General > Reset and tap Reset Keyboard Dictionary. Doing so will cause autocorrect's learning process to restart from the very beginning.
If you're a fast tap-typist ("tappist"?) and you don't want to use autocorrect at all, go to Settings > General > Keyboard and turn off the autocorrection feature.
Let's not fight anymore
Autocorrect won't suggest a replacement if it deems what you've typed to be a legitimate word. But how can you add technical terms, nonobvious place names, and other words not already in the Keyboard Dictionary to autocorrect's bank of legitimate words? You have two options.
One approach to add a word to your Keyboard Dictionary is by defining it as a semi-shortcut: Go to Settings > General > Keyboard > Add New Shortcut. In the Phrase field, type the word that you want to add, but don't type anything in the Shortcut field; then tap Save. From now on, autocorrect will not attempt to correct the spelling of that word when you type it.
The second method is even simpler; and if you ever reset your Keyboard Dictionary, it has the added benefit of preserving all of the words you've used it to designate. This method takes advantage of the fact that autocorrect accepts Contacts name entries as genuine words and won't suggest that you change them. Here's what you do: Create a new contact, and type zzz as the initial letters in the Last field to keep it sorted at the bottom of the list, where it's out of the way. Then type each of your special words, separated by spaces, into the First, Last, or Company field of the zzz contact.