This is not easy, so I always recommend my students never to divide a word at the end of a line. But in case you are wondering what the rules are, here you are:
1. Divide the word between syllables. This means, of course, that one-syllable words are never divided.
2. The hyphen goes at the end of the first line.
3. Prefixes and suffixes make natural divisions.
(The prefix is inter.)
4. There should be at least two letters plus the hyphen on the first line and three letters on the second.
6. Divide hyphenated word using the hyphen already in the word.
7. Do not divide a word at the end of a line if the parts of the word will be on two separate pages. This is hard for the reader to follow.