The cardigans that you'd except to see on your grandma are so cute at the moment! The best way to wear them is to wear them with some young looking clothes that complement the cardigan, such as skinny jeans and uggs with a simple tank top, and it's really that simple, because you want your cardigan to be the main focus of the outfit. Go for printed cardigans, cardigans with cute details (E.g. ruffles and lace), knit cardigans, any that you would put on your granny really. You can find some good cardigans in Hollister, Topshop and little local boutiques sometimes have the most beautiful cardigans.
Thanks for reading! ☺