Understand the Customer Journey: Using the customer journey map, highlight the areas where a customer gets most engaged and may benefit from a tailored offer.
Maintain Relevance: Make sure that the recommendations made are relevant to the existing status of the customer as well as what the customer might need in the future. The end result of serving up irrelevant content is to turn the customer off and see them go elsewhere.

Continuous Testing and Optimization: It is recommended to experiment with various forms of personalisation and fine-tune results from this type of advertisement. The A/B testing is exceptionally beneficial.

Integrate Across Channels: The primary lesson that could be learned from the example is that it is vital to remain as consistent as possible. The personalisation should be aligned across all the customer channels, such as emails, websites, and direct sales.
Sales Team Training: Make sure that your sales team is properly trained and has the right tools needed to incorporate personalized data into their sales propositions.

Read the article - Best Practices for Personalization in Upselling and Cross-Selling

https://salesmarkglobal.com/personalization-in-cross-selling-campaigns/