I suggest getting out. Physically moving yourself to do something else somewhere else. Go for a run. Be gone at least half an hour. Turn your phone OFF off and don't touch it. Think about nothing, or if you can't, think about your homework project. Explain it to yourself. Give yourself the lecture you would need to give to tell someone else how to do the project.
When you return, sit down somewhere other than your computer. Get some paper, again a physical object. Write out all the pieces you need for this project. Do you need to do research? If so, what pieces of information do you need to find? What are some likely sources?
Come back to your computer. Do not open your email. Do not turn on your phone. Do not open a game. Fire up your word processor and open the file - or notebook page - that has the project description in it. Review the description and make sure you're on the right track - it sucks to do a bunch of work you didn't need to.
Type up an outline of what your homework will look like. If you're answering a set of questions, type up those questions. If you're writing a paper, type up your paper's structure. Most papers need some kind of thesis, body, and conclusion. Some styles are more formal. Get the outline down and think about how you're approaching this.
Are you starting with your conclusion and trying to support it? Are you casting a wide net and gathering information to come to a conclusion? The latter is the better way to do it, but I confess I've done the former also. It's easy but it screws you up, and it's not as valuable.
Are you answering questions? Just go out there and get 'em! Finding a legitimate source is probably the hardest part. You may not be able to reference Wikipedia (although at least one study showed that Wikipedia had fewer errors than other print encyclopedias), but you can use the sources Wikipedia lists at the bottom of the page!
You might want to do the parts of your project that are easiest first. Do the fun stuff. Get something done, anything, and it makes the whole thing less imposing. That's what outlining it does, too. Your brain can encompass the project completely and there's less emotionally intimidating about it - certainly intellectually intimidating! But at least there isn't the dread of starting a project of unknown dimensions.
Finally, get something done at least, something finished. Turning in bad work is better than turning in nothing (in school anyway). Try to set aside time to review and edit it with fresh eyes before printing it or emailing it to turn it in. You'd be surprised some of the really crazy mistakes I've made in papers - whole paragraphs duplicated and moved around, obvious tpyos, etc.