does everyone speck to them on the phone first if so what questions do you ask ?
For me, it's not so much asking questions (unless it's an outcall, in which case there are lots of important questions!) but rather just having a polite and friendly conversation to make sure they are at least capable of doing the same. Can they inquire respectfully about your booking procedures, rather than going, "Give me yer address!" or, "I'll want anal and CIM, luv, or else I'd better get a discount", or anything similarly annoying/awful? Do they ask anything odd, like whether you live alone, whether you're new to the industry or whether you've had a lot of clients that day? Do they make pushy demands? Do they start trying to get free phone sex? Most of my genuine clients are amazed to hear some of the stupid and irritating things timewasters and creeps will ask over the phone or by text/email! Genuine clients 99% of the time wouldn't DREAM of being effing twats over the phone, so avoid anyone who thinks behaving that way is appropriate.
You do need to give these guys plenty of chances to put themselves on your Do Not See list - the vast majority of bad'uns seem unable to hold themselves back from doing what they do best (giving us the heebie jeebies) if you give them enough time! - and plenty of time for your instincts and gut to get a "feel" for them so that you have a better idea of whether to let this man into a private location with you.
I tend to forget how many nutjobs, or even mildy unpleasant clients, are out there because I'm so strict about vetting and only have to take a few bookings a week. I've gotten amazingly good at letting the annoyances of sorting the wheat from the chaff just slide by so I can keep my positive attitude for the good, kind, sweet & generous ones! But if I think properly, I would say I ignore or decline up to 50% of inquiries, seriously. There are so many "iffy" ones that I'm just not prepared to risk my possessions or my life by giving them an appointment. It's not complicated to see me - you just have to be a decent, normal bloke, which is sadly more than *certain* people can manage!
The safest way to work is to keep your weekly target number of bookings at a manageable level - tours and parlour work obviously excepted, especially if you're not working alone - so that you're never overwhelmed by requests and rarely have to take any bookings so last-minute that you don't get a chance to check out the client's communication-style thoroughly first. This is probably not the most lucrative way, though - despite raising my rates to keep inquiries down, I'd still have to see 10+ a week if I wanted to be one of those wealthy Belle de Jour-types, but for me, safety is paramount and once my bills are paid, I'm content!