In terms of building brand awareness, authority, and SERP visibility before the launch of your website, it would be a good idea to create a 'coming soon' landing page. Outline the core message and values of your brand, ideally include some sort of call to action, and optimise it for the most relevant keywords to your brand. This will at least provide an initial platform to get started, although link building will be a lot easier and more effective once your full site is launched.
As for link building techniques for your newly launched website, here's a really helpful article on the topic with plenty of background on the topic, as well as how to actually do it: 1and1.co.uk/digitalguide/online-marketing/search-engine-marketing/seo-basics-link-building-tips-for-good-page-ranking/
But, to summarise, it's crucial to first create quality content that has the potential to attract backlinks naturally. These are the most valuable form of backlink, so try dedicating some time to improving your blog, and include a variety of types of content - infographics, videos, informational columns, etc. It's a win-win because great content will help you rank in SERPs and build brand authority, which in turn attracts other sites to reference you.
In addition to this, guest posting (as paul suggests) is a useful, more proactive way of securing backlinks. Do some research into other sites (online magazines, blogs, etc.) in your niche and pitch them an appropriate content idea, i.e. one that will be of interest to them and beneficial for you. For certain sites, link exchanges can also be quite fruitful. The great thing is that, by selectively choosing sites to target, you have more control over the quality of your backlinks. The article I referenced goes into more detail about the importance of this - website authority, link environment, and so on.
There's a lot more to it, of course, but I hope that helps you to start with!