Be sure to do something
Definition 1 of 1
Pro Tip 1/3Importance Emphasis
Use 'be sure to' to stress the significance of doing something; it makes the action seem critical or essential. 
Be sure to study for the test—it's worth half of our grade.
Pro Tip 2/3Commitment Reminder
Conveys a strong reminder to oneself or others, almost like a commitment that should not be neglected. 
I'll be sure to call you as soon as I arrive in New York.
Pro Tip 3/3Instructional Advice
Used when giving instructions, often in manuals or guides, to highlight steps that must not be overlooked. 
Be sure to turn off the engine before checking the oil level.