Lighting can really make a big difference to an event. If you are planning on hiring a lighting crew for your event please do the research to be sure you are picking one that fits your personality.
Try and meet with the lighting crew at the venue and let them know as much as possible, as you typically do not get a "test run." That will help explain what you are looking for and help the lighting technician visualize what can and cannot be done. Also see their work especially if they have done work at the venue already. Be aware of the space you are working with. Take notice of any permanent lights or doors and windows that could affect your lighting. Another light source that is often overlooked are candles. Be sure your candle lighting is not overwhelming.
The dimming rule is to make the room about 10% to 20% darker than you think it should be, wait a few minutes for your eyes to adjust look down and see if you can still see your shoes. That's normally a good test to see if the lighting is good.
With up-lighting keep in mind the light is placed on the floor. You don't want to put that anywhere that a guest may trip on it.
Be careful with what colors you are picking. Certain shades can make guest look unattractive and can also affect how your photos come out. Generally speaking neutral and soft light colors make the best choice.
Christmas lights make a great addition to the look and feel of your wedding. Now is the time when more is better, you really can't have too many lights!
What type of lighting should you look into for a wedding? Warm-up lighting around the room, pin lighting for centerpieces, especially the tall ones, pin lighting on the cake and lighting for the band/djs and dance floor. Those simple lighting can absolutely transform a room. You can also get personalize with the lighting. Maybe having your couple monogram on the dance floor.
Last lighting thought: be sure to check the venues voltage to be sure they can handle your ideas!