Make it easy for them to buy you. Sales skills get them the first time, service brings them back. The market is very competitive, there are thousands of brilliant professionals out there working towards the same buyers you are. Often the victor is simply the one who offers ease and pleasure in the purchase. There is nothing which turns a buyer off faster than not being able to reach the speaker.
Time is of great importance.
Then constantly strive to be even better by improving delivery, content, and knowledge. Speak with a sincere, eloquent speaking style. As you speak, keep your eyes on the audience, talk to them as if they were one person. Tape yourself speaking, and listen carefully. Always practice out loud.