When first starting out online the thought is to spread yourself thin over many different sites quite quick and hope for the best, but this is not really the way you should be doing any type of online promotion, you should be spreading yourself thick instead of thin as the more you add value to your sites then you are building yourself up as an expert of high value.
People want to read high quality information from people who take themselves seriously and those who want to help others too, whatever you are good at show this first by all means and then show what others may be searching for and wanting to know how to do what you are doing and really explain it in detail, either in a report or a product you may sell on a sales page.
Adding backlinks to your online websites is the best way to go, but always do this in an organized way, instead of a random act of spam madness, you need to find other people who may want to find your information for themselves to read and find through the search engines or some other means, a group or niche related membership site or forum.
How many times have you seen a site were all they have is just banners and links and pretty much nothing else, these sites don't do well at all, they just clutter up the world wide web and quite often these sites don't get updated after a awhile and just die a quick death.
Some people seem to think once you have a website up an running, that is it, the work stops, but half of the battle is to keep it updated and driving more traffic to it at the same time - that is online marketing, the process of promoting your website to the masses, always remember that marketing never stops as long as your website is online, think about new ways to get more traffic, maybe an affiliate program for others to join related to your product, or start a forum on your topic and just talk about it in depth, the many ways are limitless.