Start by registering your domain as soon as possible. The clock starts ticking from the date of registration, so the earlier you register, the better. Choose a reputable domain registrar that is relatively inexpensive over a multiyear period. My suggestion is always Namecheap.
I generally advise against registrars like GoDaddy for this purpose because they usually offer teaser one year pricing on domains, which then renew at their typical sky high rates. This is especially important when aging a domain as the process takes months or years of time (meaning you will hold it beyond the first year).
While not a requirement, I would also suggest building your website using WordPress, as it is the most popular of the CMS tools out there, and will give you the most flexibility long term.
You should also ensure your domain name aligns with your future blog’s niche or topic. If you have a really clear idea of what your site will be about, you can pick a more specific domain.
For example, if you know you want to launch a site that has something to do with kitchen appliances and cooking, you could pick a more specific domain name (i.e. www.airfryerhacks.com or www.bestairfryerrecipes.com).
However, my general suggestion is to pick something broad enough to allow your future site to cover a wide range of niches. This is because you might change the focus of your site during the aging process or you might want to expand the scope of the content that you cover. A good example of this based on the cooking/kitchen appliance niches would be something more general and broadly brandable (i.e. www.KitchenHero.com or www.cookingwithcasey.com)