Any tips for concentrating on homework?

I am a complete and absolute failure at getting things done. I get side tracked, wether it’s just the T. V. or pretending to be hungry so I can take a study “break”. I used to have the modivation to at least start my homework, but lately, I won’t even write the first sentence or do the first math problem. I try to begin but then I see how much there is to do and I freak out and start to get stressed and just do something else instead, (for example, I decided to go on fluther rather than doing my Science homework). Does anyone have any tips on how to concentrate?