--INSERT MODE--
# Autocomplete based on N(ext) or P(revious) words:
CTRL+n
CTRL+p
# File autocompletion:
CTRL+x,CTRL+f
# Context-Aware auto-completion (for repeating lines)
CTRL+x,CTRL+n
CTRL+x,CTRL+p
VimScript book: http://learnvimscriptthehardway.stevelosh.com/