SEO has changed an awful lot over the last few years and mainly this is to do with link building; what works now is completely different to what worked a few years ago! So it is very important that you are very careful with your link building as the search engines will definitely get more strict over time and get better at detecting unnatural links. So your web site needs links to rank but if you build them badly you can find yourself in a huge amount of trouble, once you have a Penguin penalty (the Google algorithm that deals with bad links) it takes a very long time to recover as at the moment they only update it around once per year so you will have at least a year out of the rankings if you do this badly.
So it’s very important that your link building looks natural so make sure that you do not build too many too quickly and that the links are from high quality web sites. If your web site has not acquired any new links in a good amount of time then it is not going to look natural if it acquires 1000 in a few days so you should build them gradually, to start with build only one or two per week so that the build up is very gradual.
Also take a lot of care with your anchor text as it looks very unnatural if your web site has a lot of links all using the same anchor text if that anchor text is one of your target keywords. You want to make sure that your most popular anchor texts are your site name and url and then use lots of variety with the rest and so you can include keywords but just make sure that there is lots of variety with the anchor text that you use.
It is very wise to check your existing back link profile using one of the best online services which are Majestic and Ahrefs as with these you can see what your most popular anchor texts are and build links with that in mind.
Relevancy is also very important too as links from relevant web sites and so those that have the same topic as yours are worth a lot more than links from unrelated web sites and it also looks much more natural (don’t be surprised if your web site gets penalised after getting large amounts of unrelated links). Blogs that are in the same industry as your web site are excellent sources of links as you can offer to give them free content that includes your link which many will gladly take and so everybody wins.
There are online services that build links for your web site and so they are well worth a look but keep the above in mind before ordering any link building services. For example if you have an escort web site then you can use a service like Escort SEO which builds links from relevant web sites.