Basically there are 2 ways of sending reminders: through the cron and after approving the email by administrator. Use Email settings to set up the correct sending of reminders.
Transport- select Yes to transmit messages from sender to recipient.
Queue- specify a queue value when a delivery should start.
Email sender- choose a sender from drop down
Enable admin notification- select Yes in case you want to receive an admin notification when new cart was abandoned.
Admin email- specify an email where the notification will be sent to.
Default email template admin notification- choose a template for admin notification.
Before sending a reminder you have to specify the information in Rule fields. Generally you can send reminders to specific customer groups and to various stores. You’re allowed to update a product price, add a discount, set the time range, etc.
Name- enter a name for the rule.
Status- select a status.
Need admin approving- select Yes or No.
Email template- choose the email template that was created before.
Delivery date- this settings shows dates+hours+minutes.
Days- specify a number of days after an email should be sent.
Hours- define time.
Minutes- define minutes.
Customer groups- mark the customer groups the email will be sent to.
Sort order- specify the sort order.
From date- choose a date from a calendar.
To date- choose a date from a calendar.
Choose a condition from drop down to apply to the rule.
You have to fill out fields in case you need to update a price for a product in the reminder.
Apply- choose a value from drop down.
Discount amount- specify a discount number.
NB - if you need to create another one rule, you can easily do it in Magento functional by navigating to Promotions > Shopping cart price rules.