Oh well like you say onto the next one
It may help if you create a contact form like Request & Quote, Callback Request or whatever you want to call it on your website with required fields that they have to enter their full contact details etc before they can submit the form. That way helps to weed out time wasters and you have enough info as possible to go on instead of wasting a lot of your time.
Here is a very basic example what I'm on about just randomly found on the internet with required fields
http://guttercleanerlondon.co.uk/contact-us/If anyone tries to submit the form without filling in any of the fields they will see
Error!
•Name is required
•Address is required
•Phone Number is required
•Email requires a valid email address
•Message is required
That site by the way is made using wordpress.
That firm is a wee bit bigger than people think they are too so there must be money to be made clearing gutters.
Hope this helps?