Here's how I make develop a bookmarklet: I write a javascript function, pass that to Bookmarklet Builder to make a bookmarklet, add the bookmarklet to my browser, load my test webpage, test the bookmarklet, and then something doesn't work, so I try to find what's wrong and change my javascript function accordingly and the tedious cycle starts again.
How can I make this cycle less tedious?
use the firebug console to develop and test your function, and turn it into a bookmarklet once you've got it working like you want to.