No two weddings are alike but for some reason, the general things that can go wrong or that can get better for any wedding are usually associated with the dress, the decorations or the reception.
The wedding dress is probably the most important part of the wedding because unless the bride feels good about herself, the wedding might turn into a nightmare or it might not happen at all. There isn't any way to help the bride pick her dress any faster but what you should definitely do is go for regular fittings and try the dress on one day before the wedding. Bring an emergency kit to the ceremony packed with pins, needle and thread and anything else you could possibly need to deal with a dress disaster.
Try and assemble as much of the decorations as you can a day or two in advance. The flowers will be have to put out the day of the wedding but try and assemble everything else so you've got less to do on the day of the wedding.