Hyphenation can be set to your minimum character requirement, or turned off completely in your paragraph styles.
Why would you want to turn off hyphenation for 6-letter words? Your
words spacing will suffer if you do.
You can do this by unchecking the hyphenate check box in paragraph palette.
You can find paragraph palette here :- Type>Paragraph or use keyboard shortcut (ctrl+alt+t on windows)(cmd+alt+t on mac).
Place the cursor anywhere in the paragraph you want to stop hyphenation and then uncheck the hyphenate checkbox in the paragraph palette.
If you want to hyphenate only longer words, you can do this by setting the length of words in Paragraph Styles.
For this follow the following steps:-
1. Press F11.
2. Click create new style icon.
3. Double click on the newly created paragraph style.
4. Go to Hyphenation option from the list given.
Here you can make changes according to your need.