How to use 的？

Hi everybody,

A constant mystery for me is determining when 的 should be used, not used or is optional.  I wrote a text message on my cell today that said, " 我 有意的免费的旅游的机会."  Now, to me it seems clumsy to include so many 的s, but maybe I am wrong.  Does anybody know any rules for determining when to use this little guy?

Thanks