If you have a website, you absolutely must update it with your Christmas messages. Perhaps you need a dedicated Christmas page. Tell your clients what you are offering in your salon during December. Give them reasons to visit and reasons to buy.
Online gift vouchers will this year be again a good growth area but only if you work it and link to the other marketing strategies you have in place. Make it easy for people to do. They are busy. They are lazy. They might live far away from the person they are giving a gift to. This is a totally different market but a big one that you want to make sure you get a slice of.
While you are on your website looking at what Christmas changes to make, take some time to see what else needs to be updated.
Be sure to put a prompt in to remove any Christmas specific promotions after December 25th. I hate to see anything on a website that is out of date. Looks very unprofessional.
Be sure to update your Facebook, Instagram and your other social media with Christmas messages and posts. This includes your banners.