Memorable, on-brand and SEO-friendly names.
Pick short, easy-to-say names with low trademark risk. Avoid numbers and hyphens when you can.
If .com/.az is available, great; otherwise consider a brand-fit alternative TLD.
Check social usernames are free and leave room for future product lines.
After buying the domain, finish DNS, SSL and email (SPF/DKIM) the same day — it makes the brand look professional.