As you may already know SEO or Search Engine Optimisation is how your site can be picked up and ranked highly in the search engines, such as Google.
One of the key elements of SEO are links, you want to get links pointing back to your site, however not all links are the same and you want the best sort of links coming back to your site rather than any old rubbish.
The best sorts of links are ones from sites that contain similar content to your own, so if you have a fishing site you would like to see lots of links coming back from other fishing sites, you may be thinking that at this point you know you can not get lots of these links because the companies like yours are your competition and they are not likely to help you get better rankings than them.
This is where planning comes into play, you need to think about what would make a potential rival want to give you a link from his site, what do you have that he values more than a link? If you are thinking at this point that you will link back to him in exchange for his link then you would be wrong, this used to be a trick used to fool the search engines but they are onto that one and the two links would be given a very low score.
Rather than swapping links you could offer the other site an article that would be of interest to their visitors, in this article you could include a link back to your site for more information.
Now you may not be able to do this with your closest rivals but if you can do it with similar but not directly competing sites this is a very good way of getting links, however writing all the articles and contacting all the sites can be a very time consuming process so to ensure it is done effectively and correctly you should use a SEO company to get the most from your linking.