I see a lot of people providing one way link building service. These services claim that the links would be from relevant websites. Are these guys fooling the 'relevant' websites with giving reciprocal links from their own websites? I believe a lot of webmasters put 'reciprocal link exchange directories' on their sites expecting backlinks from 'similar/relevant' sites. But they end up getting scammed. Are people ready to give free 'do follow' backlinks from their established websites without a reciprocal?
you can get related backlinks by commenting on blogs in your niche. but make sure you make useful comments that adds value to the blog. no one likes to see their blog spammed. you might need to be careful with your sig. it might appear that you are endorsed by DP to offer directory submission service. mods might not like it.
I have used a few of these services and I was very disappointed with the links I received they were not high quality and I receive little or no traffic from them. Those people providing the service can get you one way links because they use a 3 way linking system. So you will get a link from site A and they will get a link from site B to link back to site A in return for your link.
You can get one-way backlinks in your own. Joining forums is one of them. Others are, blog comments, social bookmarkings, directory submission. Those are basic way on getting one-way links but you need to have time doing this.
Be very careful if you are thinking of engaging in this type of activity. I believe google frowns upon it. Roflux.
Not only do they frown upon it, they are checking for this now too.... There's tons of other ways for you to build one way backlinks.