The Rules of the Web

(1).
The basic idea behind "How to promote your website for free" is that the web is build on clusters of related sites, with connections between those clusters. Very much comparable with the situation in scientific publications. Links on the web are what citations are in scientific publications. I have no proof for this, but maybe it is a suggestion for some web research (and, yes, I would like to be mentioned in that research as a formulator of this hypothesis).

Supposing this is the case, then successful sites are sites which have many links pointing to them, directly but also in the second degree etc. Theoretically, it is possible to express this in a number: the average shortest number of links-to-follow to get from a random page to this certain page. In other words, how many links do you have to follow, starting from a random page, to get to this certain page. The lower this number, the more visitors this page gets. There is some evidence for this: comparing the Webcrawler top list of linked-to sites with the top 100 of most visited sites, it turns out that these are quite similar.

It is also possible to calculate in this figure the number of links from a certain page, when a page offers 10 links, each link would somehow count as 1/10.

The web is self-organizing by means of links. Part of the web are also deliberate organizers, such as search engines and web directories. There are other efforts to organize the web: awards, web rings and thematic link collections. Especially the large search engines are slow and conservative and rather followers then initiators. Don't ignore them, but don't count on them either. If you want to be quick (and that is important), you should also use the other web-organizers.
In fact any one with a website, containing some links is co-organizer of the web.

(2).
A second idea behind "How to promote your website for free" is that people will easier follow links from a certain page, when they like that page. Somehow this should be also measurable, but I will just work with this hypothesis. It results in the conclusion that it is best to have a link to your page on a similar site.

(3.)
The third thing is that the web is growing fast, both in number of web sites as in users. If you can keep your "share of the market", there will be a growing number of visitors to your page. As the web is growing fast, it seems better to get your share of the market quickly. Remember: competition is growing every day.

For promoting a website, these assumptions mean that it is important to find out to which clusters this site belongs and get your site listed there as soon as possible. Since there is no clear "map" of clusters, there seems to be no other way then start to shoot in the dark. This is where most promotion tips stop. But it is possible to get feedback, to see what you hit, so you can aim better next time you shoot.