One way to reward your most loyal customers is to give them a chance to order or pre-order your new products before the general public.
First you have to identify which customers are the most loyal. You might use Shopify, Repeat Customer Insights, or your own custom algorithm for that.
You'll need to then match up the size of that list with your inventory. You wouldn't want to contact a list of 10,000 loyal customers when you only have 10 units to sell. A good rule of thumb is to assume 1-5% of those customers will buy. That gives you a buffer and leaves inventory for everyone else.
(You want to have enough inventory leftover so when your marketing goes public it can attract attention from new customers)
Once you've balanced your list size to your inventory, then you can craft your messages. How they are sent (email, SMS, etc), how long of an early access, and the specifics of your message will depend on your brand. Make sure to highlight the time sensitivity of the offer though, if you don't then you're customers won't know they were getting a loyalty perk.
Done right, this can help create launch buzz and early orders for a new product. And it can solidify your customers' loyalty.
Track down which customer cohorts perform the best
Different groups of people behave differently. Repeat Customer Insights creates cohort groups for you automatically to see how your customers change over time and spot new behavior trends.