Avoid promoting products that mostly create one-time customers.
Each product you promote has the potential to create multiple orders per customer. Some products are weak and don't lead to many repeat orders, while other products get customers hooked.
Avoid promoting these dead-end products in important places (e.g. homepage, email, ad campaigns). Save them for upsells, cross-sells, or as filler.
Otherwise your wasting much of your acquisition budget on one-off customers.
Eric Davis
Analyze your customer behavior
A quick and automatic way to measure your customer behavior is with Repeat Customer Insights. It'll automatically import your Shopify data and run a number of analyses to highlight different customer behavior.