It depends on the type of block.
If it's a story block: writer's block usually stems from running the editing side of your brain at the same time as the writing side. One useful way for breaking through this is just to write without looking at what you're doing. No editing, just whatever comes to mind. You can worry about it being good later, but getting yourself going at all helps a lot.
If it's a drawing block: when I've encountered this, it's usually from over-drawing. I usually go for a walk, engage with a new piece of media, or talk to friends or my wife. I also accept that some weeks I'll just be less productive than others, so I try and do more in advance when I'm feeling more productive.
