How to build link to an authority niche site?

It's great that you're going for this strategy: targeting the easy-pickings longtail keywords for short term incoming and shooting for the overall niche authority for the long run.

I've found great results building authority sites using the traditional silo architecture.

Lets say you're overall niche is 'dog training'.

Then you figure out some medium competition keywords under this niche: 'hunting dog training', 'show dog training'. Link to these guys from your 'dog training' homepage.

Then under these, you have your easy longtail keywords like you were talking about. Under 'hunting dog training' you might have 'golden retriever hunting training'. You link to these guys from their respective parent categories.

The last part, which helps to build up the authority, is the key: link the small long tail pages back up to the home page.

Then you start your link building. Throw links to the tops of your silos: 'hunting dog training', 'show dog training'. The link juice will flow down to the easy-pickings pages and will get you quick rankings. But link juice will also continue up back to the homepage, further establishing your authority in the niche.

Works like a charm.

Research the topic of "silo structure" when it comes to creating a website and content, this will make sure you site is setup best for the search engines, but most importantly getting lot's of search engine traffic comes from having quality content that you can use to attract quality links, you can get garbage to rank however it won't stay there for long unless you've got real engagement from your visitors, so start with pleasing your visitors first and google does a pretty good job of figuring it out too..

If you want to get the site ranking highly in the SERPs, you're going to need to build backlinks. Yes, use your long tailed keywords as anchor text, along with variations of those keywords, synonyms, the URL as anchor text, etc. The backlinks should be dofollow and on high PR (page rank) pages. They will be even more powerful if they're contextual (surrounded by text related to your niche/keywords) and relevant (on sites related to your niche). Just remember to never over optimize your anchor text when building backlinks.

You should create a content around long tail keywords. I usually search them through LTP (Long Tail Pro), it is an amazing tool that will help you find hidden gems. Same time, you should start building links to your main site (blog commenting, forum posting, guest posts,...)