That best thing I found was to contact a wedding videographer in the area and work as a second or third camara for him/her for free, that way you can learn from them without the risk of messing up some ones wedding video. Also look at other wedding videos and see what they did. There are also technique videos out look at
Elite Video john cooksey is one of the best videographers out there (hes also a really nice guy, Marthas nice too) I would recomend the Advance broadcast Techniques, Digital lighting magic and Wedding videographers companion in that order the chroma key magic is also good but it over laps a lot with the digital lighting videos. You can rent these from Smartflix but you won't get any of the papers that come with them. if your like me you'll watch them over and over, all together there about 8-9 hours worth. Its fast paced and more then you can rember in one viewing. Good luck