That is a sad reality. In a perfect world every clients would be polite and nice. But it seem there is tons of peoples who just don't care.
I dunno if my way of contacting SPs or agencies is the best, but usually it goes...
Agency : Hi (booker name), its HM, could i see (sp name) on (insert day) between 1pm and 7pm, for 1h. Thanks
Indy : Hi, i saw your ads on merbs, would love to meet you on (insert day) between (insert times) for 1h, would it be possible?
If no services are listed i may ask about them, but again very politely. I seen some form of US escorts introductions and those are very elaborated, way too much for me, but i think my aproach ain't bad.
I just don't get the dudes that goes like "hey, you avail" and expect an answer...
Pretty much my way of communicating too. Short, but functional questions. And always polite. I don't write novels (and do not like reading them), but being civilized is part of my values.