Always be professional when answering the phone , ask for a name and number , and details about the work required , before you give a price.
Practice and rehearse answers / responses that clients say to you , and you to them, write them all down that you have heard over the months /years and all the new ones you hear,
Never put off calling a potential client back , ask them if have they had a chance to speak to their partner/wife etc and as mentioned above offer them some "added value" to try and secure the booking, even if they say they have booked another company , keep trying, ask how much they will be paying, what service they are having etc.
We are all price shoppers ! I always think its important to flexible with prices and services , at the end of the day I would rather do a job at a slightly reduced rate and possibly pick that client up for a number of years , and the recommendations you may gain from them, than sit at home not doing a job !