An easy tactic to increase your Average Order Value is to create a collection of low-cost products.
These will be products that are $2, $5, or maybe up to $10. You can manually curate them to include easy-to-ship and high-profit products or you can use Shopify's smart collections include everything below a set price.
Then on your cart page you call-out to them. Especially if the customer is below your free shipping threshold.
Ideally you'd add some code to say something like "You're $3.24 away from free shipping" and link to your collection. (Your theme might have that built in already. It's an easy feature for them to include)
Done right this can boost your AOV a bit without a lot of work on your side.
If you want to monitor your AOV, it's calculated as part of Repeat Customer Insights. You get your overall store-wide AOV, at different time periods, for different customer cohorts, and even based on where you acquired the customer from. It's one of the core metrics included in the analysis.
Optimize your promotion timing to save money and attention
Repeat Customer Insights will analyze a ton of customer behavior data for you, including their buying cycles.
If you knew exactly when the majority of your customers were ready to buy again, you can increase your orders and profit just by tweaking your message timing.