When you host a webinar, your focus should be on educating your audience. Be aware that they have not signed up for a sales pitch, but to learn more about the subject you specialise in. If you do have something to sell, mention it succinctly at the end but do not make it a major focus point. You may want to explain at the beginning that there will be a short sales pitch at the end. To close a sale, make sure you have the phone numbers of your participants and conduct a follow up phone call where you gauge their interest in engaging your services. You could also consider offering a one-off discount as a sweetener.