I don't believe in waiting for the muse.
Left to her own devices, the muse is easily distracted by shiny things and will waste an entire day in the contemplation of a butterfly. Or a leaf. Or a piece of cheese. I have it on good authority that the muse of writing really likes cheese.
I believe that if you show up to your desk every day and write, then the muse will see you there, be curious about what you're typing without her, and come along to join you (usually munching on a wedge of cheese).
At which point, you can seize her by the throat and insist she stay.
Eventually, she'll start showing up earlier, knowing that she can depend on you to be there. Sometimes the two of you will arrive at the door to your writing room simultaneously, and there's an awkward, "You go first." "No, after you." "Really, I insist. You first."
This awkwardness is compounded by the fact that the muse has no corporeal form and is therefore incapable of holding open the door, though she thinks she can because the muse is an eternal optimist.
I like to give the muse a corporeal form to inhabit while she's visiting. This form varies from book to book. For DRINK, SLAY, LOVE, here is what she looked like:
My muse and I find this form hilarious. What a lucky coincidence that she and I share the same sense of humor. And a fondness for cheese.
4 days until DRINK, SLAY, LOVE!