Proposals not being a surprise is quite common, and they shouldn't be a surprise. Both parties should know they want to be married before the proposal happens.
Although in my family's experience, it's usually the woman who decides to marry her bf and so she'll drop hints like taking him with her to friends' weddings, or finding ways to bring up raising a family in casual conversation, and stuff like that. Prepping him to decide to propose, and making it obvious she'll say yes.