There are definitely parts of renovations that homeowners can do without the help of a contractor, and doing some things yourself can help get the total cost of your project down. However, when you're planning to do things yourself, just make sure you have a very clear idea of what's involved before you take it on.
When my husband and I renovated our house in 2011, we installed all of the doorknobs ourselves to save a few hundred dollars in labor. It was simple to do; took us maybe an hour, and we saved a bundle. We also decided that we'd paint the interior of our new addition ourselves, though, and this turned out to be a bit of a mistake. When we said we'd paint, we were thinking about other rooms we'd painted – get some rollers and drop cloths, paint the walls, and presto! What we didn't realize was that on a new addition, there is more to paint than just the walls. There are windows and baseboards. There are doors. And there is the ceiling. A year later, we still hadn't gotten around to painting some of the trim, and we ended up paying someone to paint the ceiling, because our high ceilings were just too much for us to handle.
Doing it yourself is great; just make sure you know what you're getting yourself into before you take on construction tasks. You don't want to end up like me, staring at unpainted wood and kicking yourself!