How can I improve my concentration and attention span?

I haven’t been able to really focus for a long time. Seems like it takes forever to get started with something, and after 45 minutes or so I either get bored or distracted.

I’d chalk it up to laziness, but this seems to happen with everything; projects, video games, movies, no matter how much I enjoy what I’m doing, I get a little less than an hour before I’m looking for something else to do.

What methods or techniques can I try to improve my concentration and increase my attention span? I’m looking for anything here, be it exorcises, herbs, general ideas, anything.