To avoid being a hongo of the home page, you’ll want to insert a “Continue Reading” link after the first paragraph or two of longer posts.
If you are working in the visual editing mode, the “Insert More tag” is in the spot marked by the red arrow below.
In text mode, it’s simply the box labeled “more.”
Place your cursor where you want the jump to happen and click on the Insert More tag box. Either a dotted line labeled “more” will appear (in visual mode) or some code with the word “more” and an exclamation point (in text mode) will appear in the appropriate spot.