I really need to go back through my Android phone notes again and post them. I’ve already forgotten an rediscovered some good tips, like this (shamelessly stolen, I think from somewhere on this thread):
You can easily add words to your dictionary while typing by long pressing on the word from the suggestion bar over your virtual keyboard.
First type the word as you want it to show, then execute a long press on the word in the ‘word suggestion bar’ next to the suggested words that highlight in bold orange… this long press will automatically save it to your dictionary.
If you add a word by accident, you can remove it by going to Settings ==> Language & keyboard ==> User dictionary, scroll down to find the word you input, select it, then press Delete.