You know when it hits. It can be anytime, and many times it is not at a convenient time. But when you have inspiration, don't lose it.
For me it may be on an issue in a case. Whether I am at my desk, or in the middle of the night, I write it down. I usually use the Note app on my phone, but paper and pen still work. I have learned that if I do not do that at the time, there is a good chance my moment of brilliance will be lost. I may remember it later, but I may not.
The key is to know you have to record your thoughts when the inspiration hits. Come up with what works best for you. If not, you risk not remembering whatever fantastic thing has popped into your brain.
One way to think about it is what if you were a musician and you didn't want to record that melody that came into your head, losing a possible big hit. Or if you were an author and you lose a great plot twist for the book you're writing. We all have something equivalent in what we do for a living, or with personal; matters. So don't lose your Stairway to Heaven, or Smells Like Teen Spirit, or whatever song you could be writing.
As always, this post and others can be found on my blog, at BusinessLawGuy’s Blog.