If you find yourself struggling with those first couple of sentences, it's not the end of the world. While all of us experience a touch of writer's block from time to time, my experience has been that it all comes from one source and there is always one simple solution.

The perfection problem
In my writing, the single biggest source of frustration has always been the problem of perfectionism. There is something about the overwhelming whiteness of that empty page that says to me: "Don't put anything on here that isn't right." When I get writer's block, it's always that same exact feeling: I get a few words in my head, and then ignore them. I get a few more, and then I ignore them. Then, I get a better idea, and I second-guess it. This can go on for hours if you're not careful.

A simple solution
Just sit down and write. If, after ten minutes or so, my page is still blank, I just tell myself: "It's going to be one of those projects. Let's get working."

The truth is that sometimes you just aren't inspired, and, as far as I know, there is no way to just make inspiration come. So, when I'm staring into that abyss, with nothing falling on to the page, I simply lean into it and start working anyway.

When you just can't find your muse, you have to write, no matter what. Try outlining. If that doesn't help, I recommend writing any sentence that would fit anywhere in the project. If you have a closing line for what may eventually be the fourth paragraph, write it down immediately.

You have to get ink on paper, or dots on the screen. As soon as that happens, your brain will loosen up. Write sentence fragments. Throw one-liners onto the page. Purge from your head all of your bad ideas, too. You have to destroy the sanctity of the page, because it can ruin you.

To this day, this process has never failed me. By the time I have filled a page with nonsense, detritus and idiocy, it comes. From out of nowhere, that idea that I needed always comes.

Why does this work?
I really don't know, but I have my ideas. When you follow this process, you inadvertently take a number of important steps towards true understanding, as described by Bloom's Taxonomy. By outlining, you demonstrate a type of knowledge and comprehension. By writing fragments, listing attributes, and jotting down ideas, you are performing a type of written analysis and synthesis. Perhaps it is only after taking these steps that the mind is finally able to evaluate the problem fully.