Writing XML - learn some good habits.

You love XML and the flexibility and interoperability that it offers, but you can do some things to make your interaction with XML and the tools that you use to work with it significantly easier. Picking up some basic good habits when you work with XML will ensure that you get the most efficient use out of your XML documentations and applications.

Here are the top 10 good XML habits to adopt:
1. Define your XML and encoding
2. Use a DTD or XSD
3. Remember to validate
4. Validation isn't always the answer
5. XML structure versus attributes
6. Use XPath to find information
7. You don't always need a parser to extract information
8. When to use SAX over DOM parsing
9. When to DOM over SAX parsing
10. Use a good XML editor

For more detail see here