Your domain should be memorable and relatively short so it is recognizable and can be easily included in your marketing materials. The shorter it is, the larger it can be on your marketing materials (business cards, yard signs, print materials, etc). Even if you don't use it, we always recommend buying yourname.com if you can. You can easily forward it to the domain you actually use. Think of your area, maybe the hashtags you use in social, etc.
Keep it short so it’s easier for potential customers to remember and can be easily incorporated into your marketing efforts.
Make it broad enough that it can work for your business long-term. Overtime, you will build up domain authority, so you'll want to avoid changing your domain often.
Incorporate keywords that are relevant to your business or location when possible to help with SEO.
Avoid words that can easily be misspelled and phrases that make your domain harder to remember.
Make it unique to your business to avoid confusion for potential customers who may be inadvertently directed to another business’ website if it’s too similar.
Always avoid using trademarked words. Such as REALTOR, your franchise, etc. If you choose to use these in your domain (or email), make sure you have read and follow their guidelines for using this in your domain or emails.