I have been providing DJ entertainment at weddings now for over 10 years. I got my start at a large local company as a DJ and trained my way into being an MC through their programs and events. After working as an employee for years, I slowly started working more for myself and for other companies as a contractor.
I was able to start doing weddings on my own as I invested in equipment that was dual-purposed for both my band and DJ events. This was a conscious decision on my part since I enjoy performing in both of these ways.
I have spent years investing in high quality equipment that is capable of doing everything from small weddings and events to full bands at small to medium sized venues. I have gained a wealth of knowledge though my work as a DJ and as live sound tech for bands.
When it comes to playing music for weddings, I have a few simple "rules" that have helped me create fun events for everyone. First, I try to make sure that every song is dance-able. If a song cannot be danced to in any conceivable manner, then it's not going to be a good choice for this occasion. Second, I always try to play the hits. I play the classics that everyone will immediately recognize. Lastly, I start with the oldies and progress through the 70s, 80s, 90s, and end with modern dance hits. This last point is not a hard and fast rule, but a general outline of how the night will progress, hitting each genre for a while with slow songs in between.
For my MC involvement at weddings, I try to be as involved or as minimal as the bride and groom would like. My default sensibility as an MC favors minimalism. I will make sure everything goes smoothly and coordinate all of the scheduled events, but I don't use any gimmicks or gags that are not specifically requested. I do my best to make sure that the bride and groom are always the center of attention, and that people are enjoying the music and dancing, without making myself the focus.