Waiting for it to naturally pass usually does not turn out well for me. If I don't have a deadline, I tend to leave whatever I was writing behind in the dust while I wait for inspiration that never comes; if I do have a deadline, I don't have time to wait, so I have no choice but to keep writing.
The best defense against writer's block, I've found, happens before writer's block can even set in: planning and preparing what you're going to write. I get stuck most often when I'm writing blindly, without any idea where the story is going. Prior to last year's Nanowrimo, I decided to outline more than I ever had before, and planned out the main story arc, subplots, character backgrounds, and, most importantly, scenes. I wrote a brief summary of what should happen in each scene, and determined how many words long they should be. This all helped keep me on track; I never got lost wondering where this scene was going or where it should end or what should happen next.
Nanowrimo itself is a fantastic exercise in how to beat writer's block. You know that deadline I mentioned before? That's Nanowrimo in a nutshell: a great big looming deadline that terrorizes you to keep writing, no matter what. When you have to write 1,667 words per day for a month, you don't have time for writer's block! So, if it pops up, ignore it. Just keep writing. If you're stuck on a particular scene, skip to the next one. Or throw a new one in that you hadn't planned at all. Switch up your perspective, or start writing from a different character's point of view. Kill a character. Introduce a new character. Give your main character a grudge against someone, or an interesting personality quirk, or a bad injury. Do whatever you have to do to keep writing and to kick writer's block in the face—even if you end up editing it back to the proper perspective or deleting that extra scene, it will have done its job in keeping your creative juices flowing.
I also find that reading helps me with writer's block, because reading generally makes me want to write. Reading something within the genre I'm writing is most effective; it gets me in the right frame of mind and usually triggers new ideas or better directions to go with the scene that's tripping me up. Watching similar films helps, too. I wrote a zombie apocalypse for Nanowrimo one year and watched pretty much every zombie apocalypse film I could get my hands on the month before to get that imagery in my head.
And, talk your plot out with someone! Sometimes, all it needs is a fresh perspective. My boyfriend has helped me through a lot of tricky plot holes not only by giving me ideas and suggestions, but by asking me questions that help me figure out where, exactly, my problems lie. (Just putting this out there: I'd be happy to be a sounding board if you ever need one!)