The threshold for shooting a wedding scene is very low. Once you are proficient with the DSLR at hand, pair it with a zoom lens with good optical performance and add a flash, and you're basically set. The focus of on-site photography is on documentation rather than creativity. First and foremost, you need to record what happens and who participates, and clearly explain the environment and the sequence of time in the photos. Accomplishing these things is basically success.