Natural links one way.
This is the only one based in good content and resources. This is the safest method of link building available as to the search engines, which are in the "intent" of links. But it is also the slowest. If your site is new, then as part of its launch, subject to specialized web directories. Start with a few highly trusted directories, but no more than 10-15% of its connections in general from them. Do not overlook industry specific directories that can be paid or unpaid. They usually send highly qualified traffic and can be a real bargain. Directories will get many links at the natural site of one sense, a natural rate of growth. This combination of type and speed is very beneficial. Look for sites that would benefit from offering users of its content.

Linkbaiting, or link bait.
This is not easy, and involves creativity. But it is worth every effort. Linkbaiting regards content, videos, pictures or anything on your site that is created with the intention of increasing links to it. It is very effective in getting links, probably the cheapest too, based on the cost of the "bait" used, no negative effects of the search engines, at least not for now, since all generated links look natural . When coupled with social bookmarking, networks associated with these links add even more value for them.

Paying for links or paid links.
These links can have great benefits in the short term search. These are especially good for sites that have tons of pages of content, and have been well established online for years. In addition, these sites also have many natural links to them, again because it was well established online for years. These are not recommended for new sites. Look for sites that are highly over the issue with it, and complementary niches. A very important factor in the evaluation of these blogs, like any other, is age. And the recent "Google slap" effect the drop sites to pass the top 30 in the charts, is that primarily affects those who make the purchase of strong bonds.

bad links and their effects.
Outbound links play an important role in the search engines to determine how your "neighborhood" is. bad neighborhoods affect your search engine rankings. Things such as FFA (Free For All) link pages, link farms, etc, fall into this category. Note that this has nothing to do with the pages into the supplemental index. That is not the type of punishment of these links because of their site. And the number of links is great evil in mind. A small number of them do not result in a penalty, but make sure your site is not related in any way to reference standards.