How much of each entry shows in the feed of my journal?

By default, the feed of your journal shows all text before a cut tag and then a link to the entry.

You can change this for your journal, or for a community you're the admin of, at the Privacy tab of the Account Settings page, under the setting "Syndication Level". (To make the change for a community you admin, choose the community in the drop-down box next to "Work As" and hit the button labeled "Switch".) The options are:

Full Text

Displays full text of each entry, including everything after a cut tag

Cut Tag

Displays the entry up to the first cut tag, along with a link to the entry.

Brief Summary

Contains only the title of the entry and the first few lines, then a link to the entry.

Title Only

Contains only the entry's title and a link to the entry.

If you set your feeds to display only a summary or title, this will make it harder for people who use your feed to read your journal. Be sure this is what you want to do before making the change!