Searchenginegenie.com

The only "pop up" we use on our website is for Chat. A Chat window pops up 20 seconds after a visitor has been on a web page.

An email opt-in form is fine. For instance after 10-20sec. But there are tons of different possibilities so that your visitors can be involved more subtle into your website, without forgetting it that fast. But take care not to disturb them with too "aggressive" pop-ups, which can be very annoying. Especially when they appear over and over again.