The best thing to do is to name something specific that you did together. Either that, or jot down some of her favorite traits & name a different one every month. Could even be that you noticed how she handled a particular situation or that she was kind to you or to someone else & say exactly what the circumstances were. Can also say how she looks good in a certain color or style, but her specific traits are more important than how she looks & should be the main priority for mentioning to her. You could also say how happy she looks lately or how happy you are that she's doing well in school or in other endeavors. If she tells you about a certain book or movie that you especially like, then tell her your appreciation of that. Now you should be able to see what I mean by specific & will have many things to say for months to come with more of them coming along with each passing day.