Not working with a budget - You should have a budget before you start to plan your wedding. Not having a budget often results in wasting of money. Be careful you're not spending on what you don't need to be spending money on. Budgeting will help you afford your wedding!
Not hiring wedding professionals - You need to rely on experienced experts if you want a stress-free wedding. There are wedding professionals to fit every budget. Please don't asking your friend's to play professionals, they are supposed to be guests at your wedding. You may think you are saving money, but this will only bring you pain. With weddings you don't get a chance to get it right, so check references to ensure you've picked the right professional.
Not incorporating personality - A wedding is all about the bride and the groom, it should reflect their lives. It's not compulsory to have a theme but when people walk into your wedding, they should feel they are attending your wedding and not a recurrence of the last wedding they attended. Im tired of listening to the same Bible passages at ceremonies or seeing the same type of decor at wedding receptions. Be creative, be yourself!