Links: internal, inbound, outbound
As well as the technical aspects about how a web page is built, another important area is link development - that is other web sites that link to yours. These inbound links do two things. It means that people who visit another web site can see the link, click it and come to your site. Secondly, the search engines see this link to your site and your site gets recognised. The best links are from other well ranked sites, those that are relevant and sites that are in the same topical area.
Outbound links are useful too. These are added to various pages on a web site to assist browsers in finding information that will be of help. This does not dilute your web site but in fact helps the search engines know that you are providing your site visitors with this information. Such links to well considered sites like the BBC (Rank 8-9 in Google) help best.
Internal page links are vital too as they help your browsers find other pages in your site and depending on how they are coded, will help in SEO.
However, reciprocal links are not as valuable as they once were. They basically balance each other out as far as the search engines are concerned but must still be done. Links now are the principal element in getting good positions on the engines. You can help get links yourself by finding like minded people who will link to/from you.
Again this all needs proper management.