What is appropriate bridal shower gift etiquette?

My boyfriend’s best friend is getting married in October, and I have just received an invitation to the bridal shower. I take it from the name of the event that the idea is to “shower” the bride with gifts.

I have only met the bride once, and have not been included on any registries. Is the socially appropriate thing to do here to randomly guess at a gift? Bring something generic? Will it be a terrible faux pas to show up empty handed? I don’t know these people very well but they are very important to my boyfriend so I don’t want to do anything stupid.