The holidays and gift giving can be stressful, but I have been using three guidelines for buying gifts for years and they are just about fool proof.
If you are buying jewelry purchase the "type" of jewelry the person wears most often. Doing so will increase the chances that they will actually wear it. Many people tend to buy diamond jewelry as a gift, but the recipient doesn't see it as everyday jewelry.
Also, think about the person's likes and interests. If they are an artist get them art supplies, if they like sports buy them tickets to a sporting event.
Third, if you overhear them say they would like to have something, and they are not going to buy it themselves, get it for them. Gifts are a hit when it's something a person really wants.
I hope these tips help. Let me know, in the comments, if you use any or all of them.