In SEO we have a main concern of link building and we have thousand of free link building sites.Which sites should I trust?
Check out it's backlinks, where it comes from. check the PR, also check the domain age. Whether it is indexed in Google or banned. etc
There is no fixed parameters to detect spam links but most common parameters are: 1. Generally auto approval links are considered spam. 2. Low PA, DA, PR, not indexed from long time is spam. 3. Links from irrelevant sites means links from other niche sites. Example If health site get link from online money making site then it is getting link from irrelevant site.
Check their alexa ranking and authority of website.Collect these websites and remove links via disavow tool.
I think most of you understand the question of OP wrong. There are sites where you can enter your site, and they will go out and "build backlinks". Which ones can you trust? They mostly just go out and insert your website into spammy directories, which carry zero value, you will end up hurting your site or it just won't matter, and you will be subscribed to 20 new newsletter with your e-mail. I suggest you don't trust any of these sites and instead go build some backlinks yourself, manually or automated (care with automatization). Try quality directories of your niche, social bookmarking sites and maybe create some blogs and schedule some content to post, interlink them with your profiles. Some sites you might wan't to register (not all of them are do-follow, but in my experience, they all help) twitter, facebook page, google+, gravatar, stumbleupon, delicious, blogger.com, wordpress.com, pinterest, tumblr, linkedin, about.me, livejournal. hope that helps
I think you need to upgrade your knowledge about SEO first. None of the above tactics works in todays world if you want to build your site's trust flow & authority. Others are right, if you want to check bad links, you need to extract their website's backlinks data first, sort the quality & relevancy vs quantity and then decide if it's good to go with or not.
I think you should read the question and my answer again. The methods I described DO build your trust flow and authority, submitting to "backlink" sites, do not. Either you understand me wrong, or you need to update your seo knowledge, Google goes more and more itno the entity-based model. OP asked which "backlink" websites work, and I said none of them, cause they just submit your site to shity directories (which doesn't work anymore), I rest my point, and I tested it myself. Nobody ask about checking bad backlinks, you can tell her a 5th time to analyze and sort by relevancy, but it's not what she asked.