Here's a very small tutorial showing something I use quite a bit when designing with inkscape. When I scan a drawing and then use the trace function in inkscape to convert the lines to vectors, the lines are often quite bumpy. Sometimes that's fine, but often I want smoother lines, and more importantly, I want less nodes on the path so that its easier to clean up and edit.
Step one: select the object, making sure you have the "edit path by nodes" button activated, so that you can see all the nodes.
Step two: path - simplify, or Ctrl + L
Step three: this reduces the number of nodes while keeping the shape of the object basically the same.
Step four: zoom in and tweak the remaining nodes until the object is the shape you want.
Two things I've noticed while doing this:
If you select a number of objects and try to simplify them at the same time it doesn't work nearly as well. The paths end up looking like an abstract mess. However, if you just select one object at a time, the shape stays basically the same. You do have to be careful though, since sometimes this will delete so many nodes that your object changes shape drastically.
When I scan a drawing to convert it to vectors in inkscape, it helps a lot if I first slightly blur the picture before performing the trace in inkscape. This smooths the lines before the actual trace, meaning there is less clean up / simplification of paths needed and also results in smaller, easier to handle files.
ps. the examples are from a new design I'm working on (yes, thats me reading a book in my living room)