My mom owns a spa and I have been working or managing for almost 4 years now. For weddings, you will probably pay a little more for your hair and make up. 10-15% is generally a good range for a tip, but since it's a wedding, a lot of people do 20% especially if they really enjoyed the experience with the stylists and loved their work. Also consider the type of style and how intricate. If you are doing a simple all over curl and pinned back, and its not a lot of work, 15% is probably okay. The more intricate and the more time spent, you might give them a little more gratuity.