1) it the tag repeats only once then it should be converted to an attribute, for example:
- name, latitude, longitude, etc.
2) shorten the tag names, but don't go to far so it is still human readable
3) compress (zip) XML files when transferring them over a network
1) put each attribute on separate line, white space does not cost when compressed
2) extend line length to at least 120 characters for readability, your window size most likely allows for more