Autocomplete reflects real, current search behavior in the exact words people use, which makes it one of the most reliable free sources of long-tail keyword ideas.
Type Your Seed Term and Watch What Appears
The suggestions that populate as you type are drawn directly from actual search patterns, not guesses, which is exactly the raw material long-tail research needs.
Add a Letter at a Time for More Depth
Appending each letter of the alphabet after your seed term surfaces a much wider set of suggestions than the handful shown for the bare term alone.
Don't Stop at the First Layer
Take a promising suggestion and run it back through autocomplete again — long-tail research often goes several layers deep before it's exhausted.
Next step: Use the Longtail Keywords Tool to turn the alphabet-expanded suggestions you find into an organized long-tail keyword list.