Firstly warm wishes for the to be couple. These are exciting in one's life and I said this from personal experience. The first thing that pops up is how do I start planning the wedding and from where to begin it. Grab a piece paper/note book to jot down the essentials and these noting will be your rough wedding planning requirement list.
It all boils down to budget whether it's purchasing a car or splurging on the wedding. You will have to be clear of the resources that are available you to. Mark your expenses down by at least 15-25% less so that later on unforeseen expensive do not out you in a fix. You can start your wedding planning from here onwards.
Thereafter what is of utmost importance is whether you plan to arrange you wedding yourself or you would like a professional to plan it for you. Take into consideration your work schedules, if you schedules do not permit you such freedom them it is advised that hiring a professional shall be good.
The professional does the planning for you right from starch and will be responsible for details and any problem that goes with planning. But in case you have a tight budget then its better to do the wedding planning yourself as professional can be expensive proposition.
It is very necessary that you plan your wedding step-by-step even if you hire a professional to help you or you are doing it yourself. Wondering where to find that wedding guide? Incase you have hired a wedding planned then they will provide you one. If not then bridal salons and bookstore do have them.
And the Internet is always there. Sites like theknot.com & more such give wedding planning guides for free. While if you like to find more options and search extensively the type "free wedding planning guide" on Google. Further reference can be taken from a guidebook on wedding preparations. Reading a guidebook may lead to newer and exciting ideas on planning your wedding.
It is also important to be prepared emotionally. You can visit premarital counseling to overcome all the problems during the wedding planning and after it.
This question was asked on the wiki: Wedding Planning Wiki.