Every once in awhile I will take a reception music gig. While the "art" of background music for dinner events and receptions has often been dubbed as simply a mindless sight-reading gig to make more money on the side, they can be an amazing opportunity for you and your true art. As a pianist, I am lucky to have multitudes of pieces written for my instrument, and popular tunes written for string quartets, for example, have often already been arranged for the keyboard. With enough music for many lifetimes, reception music gigs could be the perfect opportunity to discover new music for yourself and your audience.
1. Know your restrictions
How long do you need music for? I generally prepare 30 minutes of music -- usually a collection of 12-15 short movements or pieces. If their event is longer, I take a break and reorder the same selections. Because you're not playing pop music, I find that people often enjoy having multiple hearings of pieces they don't often have the opportunity to hear live.
What kind of instrument are you playing on? Playing a grand piano is the best-case scenario, but occasionally I'll play on an upright or on an electric keyboard. When that happens, I select music to make use of the timbres of these instruments, rather than try to play a Chopin nocturne on a honky tonk upright.
2. Know your audiences
Who is hosting the event? Is there a theme? How many people will be there? It's important to be able to gauge what kind of an event you'll be playing for, so you can know the general mood and ambiance they'd prefer (mostly serene, or uplifting, or celebratory?), and so you can personalize the music. I just played an event honoring some visitors from China, so I made sure to add some traditional Chinese folk melody arrangements into the mix!
3. Spend time in the music library
The more music you are familiar with, the better variety you can get with any program - whether music for a reception or for your own solo recital. I often draw from my own repertoire list, looking for movements from larger works or short stand-alone pieces (preludes, nocturnes, waltzes, and other character pieces). As in a good recital program, certain variety is good (music of different styles), but make sure they all fit the overall theme/mood. If you don't have access to a music library, imslp.org takes a lot of sifting through, but it can be a great source.
Keep in mind that while "The Wind Beneath My Wings" certainly is fitting for a wedding reception, you have the opportunity to revive transcriptions of Robert Schumann's songs for Clara instead. I'd also personally rather spend $0 learning these selections than $20 sight-reading numbers from this book.
4. Be flexible and prepared
I often prepare a couple of extra numbers, and extra sight-readable scores JUST in case the mood/instrument isn't what you expected it to be. Also, because you're the one setting the mood, always be attentive to the feel of the room and chose to play something more upbeat if crickets are chirping.
While it definitely takes more time to curate a unique program for an event, it ends up being a more meaningful experience for event attendees, AND you have an excuse to learn and perform pieces you've wanted to learn.