Who knows sites that do external linking really well?

I am starting a small test to figure out if adding helpful and trustworthy links to articles can help them rank better. I have seen mixed opinions about it so I thought I would try it out myself. I plan to use a few sites for this.

I need to find five or ten sites that handle external linking in a way that really works. Things like who they link to, how the anchor text looks, and if the content they link to is promotional, informative, or maybe government and educational sites only.

Can anyone suggest some good sites that you think do external linking in the right way? I would really appreciate it. If you share your thoughts, I will also share the test results when it is done in about 4 to 6 weeks.

A lot of freelancers, agencies and sometimes site owners handle it directly.

EdwardGenesis said:
A lot of freelancers, agencies and sometimes site owners handle it directly.

But how do I know if they are actually good or if they are just trying to take my money without helping?

@Peter
Check the websites they link your site to and see if the links are legit and relevant.

@Peter
It is simple, just take a look at the site they place the link on. You can usually tell if it is a solid website.