I found some people said if you want to build backlinks, you should go to the related website,but which site is related with yours? For example, if my site is an b2c, i sell electronic gadgets online, it that mean i need to some electronic forum?Should i go to some forum,just like digitalpoint? Some SEO sites?
You should go to "Google" Search for something like "electronic gadgets blogs", "electronic gadgets forums", and other websites that are related to your niche.
Try to input your main keywords https://adwords.google.com/select/KeywordToolExternal and check the related keywords. Search on google for this keyword and try to get backlinks from the sites that appear from search results. You can use trackback, commenting, blogroll, link exchange or any other methods to get a backlink from a related site. In your case, forum that is related to electronics, gadget, mobile, would work best. Try to get involve in dofollow forums, blogs, article directory, social bookmarking and try to get anchored keyword backlinks.
Getting backlinks from Electronics gadget/selling sites consider as 'quality backlink' for your site. And also links from electronics forum, electronic niche directories, related Bookmarking sites and other relevant blog sites will give quality backlinks to your site.
Yeah finding the right niche to your site can really help you to build your good links. But sometimes, it hard to find an active forum that related to you.
This helps to get more PR, as you are getting links from relevant source. As well as this helps to get more SERP Yes, this too help, as you are getting backlinks from some good sites, this will help you to get more SERP.
So i should get links from high pr website whatever is it relevant with my site and other site that relevant with my site,right?