A good website will convert between 1-5% of the website visitors to leads. To convert the visitor into a lead, you need to get them viewing a landing page which will have a form on it. On the landing page, compelling text needs to be written to convince the user to provide you with their details, in exchange for an offer, e.g. an eBook on improving you online marketing. A good landing page will convert between 20-30% of page views to submissions, e.g. 100 views of the landing page could lead to a 30 new leads.
To get the user to view the landing page, images and buttons called "Call to Actions" or CTAs are included on the website. They will be placed within text, or at the side of text, to increase the number of opportunities for the website visitor to view the landing page.
Remember: after the website visitor has filled in and submitted the form, make sure you provide them with the promised offer - not doing so is a sure fire way to make sure you don't work with them!