Anyone that owns a site, or multiple sites will know how important it is to get links going back to your site to improve its rank, and therefore organic traffic. What you may not be aware of is that it can almost be detrimental to your site if you simply start blasting it with links. You may have heard the term quality Vs quantity before, but I wanted to reiterate here for your benefit.
When looking for backlinks for your money, or main site, it is more prudent to get links back to it that actually have some relevance. The searches engine algorithms will invariably look more favourably upon links which are from sites that A) have Authority, and B) are directly related to your money site in some way. As an example, if you have your main site on dog grooming tips, and you have backlinks from wrestling sites, then these two categories are not exactly related in any way. A human, and now days the search engines will ponder its relevance, and may even harm your current rankings as a result. To ensure that you have a chance of getting better rankings for your site, it is better practise to have less links (as long as they are relevant, and from sites which have a higher PR status).
With regards to your overall search engine rankings, if your main site has a plethora of dodgy links linking to it, you are not likely to be able to rank very highly. Having said that, if you are going to go down that path, then it is prudent to do so on the likes of web 2.0 properties. The simple reason being is that these sites are so used to having many others linking in, that it will look more natural from a search engine perspective.
The most effective method for ranking websites quickly (disclaimer: bear in mind that the search engines constantly update their algorithms, and therefore this method may well change in future) is If you are able to find some recently expired domains, with some form of PR ranking still on them. These are prime real estate to help get your money site ranked. You can usually pick these up for the normal $5-$10 domain price. From there, if you put up a simple site, with some content that is relevant to your money site, and link back to your money site from these then that is how you will be able to rank higher in no time. Even in a competitive niche this tends to work.
One tip I would suggest with this method is to keep building your links. You may find that if you have a few high PR sites linking back to your site, and you start to gain rankings, the links that got the expired domain to where they currently are may start to disappear. It is important to continue building links to these sites, and to your money site after it has been ranked to where you want it.