I think the biggest comparison is that you have to treat your customers right. That means that you have to promote products that have real value. You also have to figure out a way to retain customers. It's much easier to sell someone a second time - especially if you gave them good value the first time.
Customer service plays a big role in attracting and maintaining your client base. A little communication and followup can go a long way. Try to under-sell and over-deliver. Never make a promise that you can't keep. It's always better to go over the expectations of a customer.
In my eyes it is the same like doing offline biz. The only difference is you don't need much money to start. it is the same process: advertising (every link is advertising) - getting visitors - present offer or service - sell - customer loyality.