Paid advertising. Advertising online is very simple with tools such as Google AdWords. It allows you to appear at the top or side of the main search results for a fee. Be careful with your budget and again, make sure you get these visitors on your list to be really cost effective.
When you’ve implemented a range of these activities to build your list, look at which ones are producing the best results for your particular business. Then step up those activities and let go of some of the lower performing options.