There are many strategies you can follow to generate leads with a webinar:
As soon as a person register for your webinar, send them a thank you mail and a confirmation mail. Sending this is not only good manners, but will also help get a confirmation from the registrant side.
Choose an appropriate day and time for hosting a webinar. Look for when you will receive the most traffic. To maximize the attendee rate, experiment with different days and time slots and learn the conversion and attendee rates.