If you want to get new customers in your CRM use the Web To Lead Form.
To create new web to lead form, from the main admin menu navigate to Setup->Leads->Web To Lead.
First you must create a source and status in the Leads area. Then click Web To Lead and create you lead.
After you input this information click save and then it will take you to your lead page where you can customize it. If you need more inputs, you can create them at (setup, custom fields)
Create your form and then click Integration code. Grab the link and send that out to your clients or put it on your website. The Iframe won't work due to security reasons.