You have to ask your wedding planner for testimonial and emails or phone numbers from some of their "happy" brides.
It is a must to do at least one phone call or have a conversation via Skype, there has to be a "click" between you both since your wedding planner will become your ears, eyes and will look always for your interests here!
When I personally look for a certain service I look for academy awards, certificates, diplomas or a career in whatever they are doing in case they have not enough experience.
Also, PLEASE you have to make sure that the photos they are showing you are really theirs and not from the internet or someone else photos, that is a MUST!
In this forum you will find a lot of reliable wedding coordinators:
Besides, there is an association of wedding coordinators in the area (ACIBEP), that is there to help, control, and keep updated all wedding planners in the area.
Good Luck in your search!