Discuss ahead of time the thought of getting married in the future. Make sure marriage is something you both want and are ready for.
Having said that, still make it a surprise. Find a moment when she isn’t expecting a proposal. Think of a private, meaningful spot to ask, perhaps at the scene of your first date, over a romantic dinner, or perhaps while strolling through a park.
Be prepared. Those words “Will you marry me?” are huge, and by practicing it a few times will allow you to feel more at ease and less nervous.
Know ahead of time if she would like to pick out the engagement ring or if she would like it to be a surprise. This is where a dear friend or family member can help you out. Ask to have them casually bring up in conversation whether she would prefer to choose or be surprised.
Tell her why you would like to marry her. Explain what marriage means to you, what she means to you and what you hope for the future to be like as a married couple.