My understanding is most couples now set up a gift register, so it's just a matter of picking stuff off that list. I'd check for one of those first.
As a bride-to-be who is currently beginning to receive gifts, please use the gift register. Yes, it can seem kind of strange and out of place to pick a gift out, but it is the best way. When we registered, we registered for stuff we do not own. That is what they are there for so you do not buy something that they already own.
However, if you very close to the bride and groom, then you are allowed to give something more personal. Most registry items are for kitchenware or basic items you need around the house. You wouldn't give a vacuum to somebody you love getting married in the first place. Then, you can buy them something sentimental and from the heart. For example, one of my bridesmaids already gave me her gift and she didn't use any of my registries.
So, it all depends on how close you are to this 'good friend'.