one more

[aviscowboy]

any good tips on how to build a good site management system?

[sid]

thorough analysis of what you need and decent programming skills.

[drawmack]

with good coding practices

vague question = vague answer

there are plenty of open source CMS's out there use a couple of them mark good points and bad points then try to build one that incorporates as many of the good points as possible while eliminating as many of the bad points as possible.