So as someone who did NANOWRIMO twice and made it a goal to get about 1500 words a day, this is easy, but the Nano forums won't be the place to look.
The reason why is NaNo is set up to write 50,000 words in 30 days as a goal, so their tips and tricks work for increasing a word count above all else. The trick you need to do is two fold:
So you're lucky in wanting only 500 words per day... that's easy. I did 1500, and that's rougher. For me, I had to chunk it up into three chunks of writing per day: first was 500 during my lunch break. Second was 500 when I got home. Third was 500 after dinner. If you know what you're writing about, 500 words is about 30 minutes... which was my lunch break time. I ate a lot of lonely meals at my desk instead of the cafeteria.
The second trick is a bit backwards but...
Fudge It (I'm a Poet and didn't know it):
Essentially, a set word count per day is not a hard requirement. You will never get it right on the money. Instead, try to write as close to 500 words as you can while keeping within the scene, or complete thought. Always aim to finish the scene, even if you write 627 words to do it... or 482 words.... and if the scene needs to be broken up, at least go to the major change in the scene tempo (since mine were action heavy, I always would break right as the speed of the scene was about to shift... either the dramatic bit of witty dialog was dropped just before the melee was about to happen, or the last punch was thrown and the baddie falls to the floor). This way you're ready to break having concluded the story and ready to move on and use your break time to plot out the next scene. Don't worry about making exact word counts when you get into writing... worry about adding the next full set of details to your work you need.
Just to prove a point, this answer is 459 words long (including numbers) and took me less than 20 minutes to write most of it. I could easlily ad a little more to bring it over the limit, but that might just as easily prove my point wrong.
The final guide line actually comes from NANO. Don't look back. Do your editing when you have a finished product, not mid writing. Keep moving forward, then the writing is done, set it aside and look at the things you need to add or omit from the document to make it work.