There are services that you can pay for to help you develop your email marketing campaigns, but I think that it is really easy for small business owners to do it themselves once they get the hang of it!
The first step is probably the most important. You have to gather those email addresses! Put a newsletter sign up on your website, and allow customers to give you their addresses. Have sign up sheets at your place of business and let your customers know that you will be sharing special offers with them via email! Collect business cards and information from whoever you can, whenever you can! Another great way is to install a pop up invitation on your site that allows anyone that visits to opt in to your email lists!
The same goes for social media. Ask your customers to follow you on Twitter and Facebook. Put buttons on your website to make it easy for them to join, and have them share with their friends! The results can be staggering what a few "shares" can get you!
In my opinion the best thing about this type of email/social media marketing is that your customers are opting IN! You know that they WANT to hear what you have to say, this is not "cold calling"! You are talking directly to people who are interested in your company and what you have to offer! That kind of information is priceless!
Post as much as your schedule allows, but don't over post! That will have people "unfriending" you -and fast! I would say a few times a week should be a good rule of thumb! Offer discounts and deals, let them know about sales and new products, anything that you want them to know!
Email and Social Media Marketing are absolutely unparalleled in today's business world, and once you get on the bandwagon, you will see how profitable in can truly be!