I'd bet that the most common mistake inexperienced bakers make when tackling rustic breads is that they keep the doughs too dry.
"You should be able to knead and handle them easily, right?"
Rustic breads require very high levels of hydration, anywhere from 60% to 75%. That means for every pound or kilogram of flour you use, expect to use almost 3/4ths of a pound or kilogram of water.
A dough this wet is quite difficult to handle and knead. The autolyse method I mentioned in the previous tip can cut down on the amount of kneading you need to do significantly. A stand mixer can, obviously, keep your hands from getting so messy, as can keeping your hands wet and using a bench scraper to remove the dough from your work surface. But when you are making doughs this wet you simply need to resign yourself to the fact that you are going to lose some dough when it gets stuck to the bowl, your hands, or the work surface.
"How can you possibly expect to shape a dough that wet?" you ask. That takes us to our next trick...