[visual mode] - with selected lines
gq             - format text so that it fits in whatever :set textwidth was set

[commands]
:spell [word]  - adds a word to the current dictionary (no mistake any more)
:set list      - display non printable characters
:retab         - replaces tabs with spaces
:set expandtab - in insert mode: replace tab with spaces   

[navigation]
<CTRL-]>       - go to tag under the cursor (help links as well)
<CTRL-T>       - return back from tag under the cursor