Another thing to add, if the client is forgetful, missing emails and just plain lazy. Drop it! I've had clients that are just too dumb or too lazy to their emails that I have to check it for them, and show it to them twice.
Another thing is, some clients now will give you a price. Not a price range that you can work out, but a fixed price for you to say yes or no.
A client contacted me to design a custom responsive wordpress theme for his niche sites, prices per theme? $15, when I asked him where did he get the prices, he said that it's the standard prices for those now. That's the time I lost it!
Some clients will compare prices with you and newbies, that's when I asked them this "If you wanted your tooth fix, would you rather go to a dental student or a certified dentist?"
Most of them don't even reply, lol!