For me it depends on the provider and circumstance.
I have a couple regulars who give me a shout before they post travel plans. I appreciate this as it gives me the opportunity to book them while they are available.
Some guys reach out when I've looked at their profiles. I usually explain that I'm traveling to their area soon and was checking out various providers. Where it goes from there depends upon their response, if any.
Out of the blue messages usually don't get much of a response from me. That said, I once received a message from a guy who had checked out the reviews of local providers and hit up reviewers based on who he felt would be open to his looks and style. I met up with him figuring if he was smart enough to do that level of research he was worth checking out. He was a good match.