A makeup artist is no different from any other type of "artist" you hire for your wedding day (photography, videographer, musicians, etc).  If you are making room in your budget for a makeup artist, it's important to hire somebody with bridal makeup experience, who can provide you with samples of their work and has decent reviews from their former clients.  

I've had some brides tell me that their makeup artists tell them to bring their own makeup, and they will simply apply it for them. This would be the equivalent of me, a photographer, showing up to a wedding and expecting the bride to provide me with whichever camera she felt was best.  This should be a red flag.  A skilled makeup artist only uses cosmetic brands they know and trust!  They have invested in their makeup collections and know the products that will stand up to all-day wear, even through the tears and the "glistening" (cause we all know girls don't sweat ;) lol)!  

Most makeup artists will provide either a consultation or a makeup trial.  Some are offered complimentary with booking, while others are offered at an additional cost.  Either way- it's a good idea to take advantage of them to ensure there are no surprises on your wedding day!  

Last but not least, it's important that your makeup artist is using products that don't contain SPF.  While SPF is ideal for daily sun protection, you don't want to use it on your wedding day.  As much as I try to avoid using it, there are times throughout a wedding day when I may need to use my camera flash.  When the flash fires, the SPF in a makeup will block the light on your skin and create a mask effect, making it easy to see where your makeup ends and your true skin tone begins.