I'll pass on two pieces of advice I received years ago for you to think about whenever you are ready to start charging for your services.
The first is that any amount you charge must be enough to pay for another photographer to shoot the event if you cannot do it. If you are injured the night before the wedding or if you suffer some other disaster that prevents you from shooting, you must be able to arrange and pay for a backup photographer.
The second is to value your time and charge for it. The work will not stop after the wedding ceremony and if you will be spending hours on retouching, framing, and album creation, you need to charge for your time.
My personal approach to pricing would be to do some research first and find out what photographers in your area are charging. This information will ensure that your prices will not be at the extreme ends of the range, or completely off the scale.
Next, estimate the maximum amount of weddings or events you could shoot in a year. If you live in a northern city, you may only have 25 weekends each year to photograph weddings, but if you live in the south, you may be able to shoot all year.
Then you should calculate your annual living expenses and costs. You should approach photography as a professional endeavor that will support you. When figuring your living expenses, assume you will have to pay for your own healthcare and account for the expense. Divide this annual figure by the maximum number of weddings in a year.
Next, you should calculate your annual fixed costs for the business assuming you shoot every weekend you can. You will need to pay for insurance, promotion, taxes, leasing or renting a location for the business or a place to meet with clients, and also equipment depreciation. Divide your annual costs by the maximum number of weddings you plan to shoot in a year. This is your fixed cost per wedding.
Next, calculate the cost of supplies needed for each individual wedding. Will you offer packages with prints included? Will you include any albums in the package? You'll need to figure out these costs. Include transportation costs and any other expense incurred in the act of shooting the wedding. If you do not shoot a wedding, these costs would not be incurred. These costs are the variable costs per wedding.
Finally, add up your fixed and variable costs, and decide on your markup percentage. Your markup should be enough to support yourself and pay your living expenses if you shoot every available weekend. Check your figure against what other professionals in your area charge, and adjust if necessary. It may not be possible to support yourself by shooting weddings at the market rate in your area, and most professionals do portraits and other events in addition to weddings. When determining a final price, you should also assume your services will not be in as much demand as established and experienced professionals and price accordingly. If you find yourself with more work than you can handle, the demand for your services is high and you should raise your prices and if demand for your services is low, you should lower your prices.
Do this process even if you only plan to shoot one or two weddings per year. If you approach it as a serious business, and price your services accordingly, you will help keep the value of the services in the market higher and you will be helping the other photographers in your area maintain their prices and support themselves. Undercutting the market prices drives down prices for everyone and will hurt you in the long run.
As I said, this is my personal approach, based on some experience shooting weddings professionally and reading business books, but I do not own my own business. If any professionals have ideas for improvement or constructive criticism, I would be very interested in hearing suggestions.