How effective to develop external links from different category websites for organic search engine ranking?

I was working on Virtual Personal Assistant keyword and my site is on no.1 in Google organic search.

During link building campaign: I had developed external links from different categories websites.

I don't know due to this strategy my site is on no.1 or not. Because, when I worked on this website I was SEO trainee. On that time I just aware about 2 browsers - Mozilla & IE.

I want to know current situation for this stuff. Can it help me now or not?