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You'll always be safe with the garden variety type proposing. Take her out to dinner and slip the ring into her drink when she sees it, you kneel and bla bla bla. Again, you could do it more quietly by taking to some weekend trip, and whenever the moment presents itself, you tell her she's the best thing that ever happened to you and bla bla bla, then you propose. Better still you can come up with something really unique and make it a special moment for both of you.