Conversion is getting a visitor to take action – like taking them from browsing your site to booking an appointment or making a purchase. Pop-ups, paywalls, ads, etc. (outside of necessary notifications), while good for initial engagement, can quickly become deterrents and hurt your conversion rates. This applies to small businesses and nonprofits alike. Make it seamless and easy with minimal clicks to get their information and process that sale or donation.
Bonus Tip: Check to see how many confirmation emails are being sent. There may be multiples: some from your site and another from a payment processor. Also, allow them to opt in to your marketing newsletter. Drip marketing is great, but I will unsubscribe immediately if I get 40 follow-up emails after the transaction.
Get out of your own way.