A celebration of life program differs from a traditional memorial service or funeral in the sense that it is far less formal. These gatherings are typically more like a party than a service, with loved ones of the deceased gathering not to mourn death, but to celebrate the deceased's life.
Things to Avoid
When planning a celebration of life, it's easy to fall into the pattern of mimicking funerals or memorial services. A celebration of life doesn't need a prayer or scripture reading (unless the deceased would have wanted one) and doesn't require a rigid set-up of chairs all facing a podium or focal point. And while it is fine to display a photo of the deceased, it should be a happy photo and shouldn't indicate mourning (no black ribbon on the frame or arrangement of funeral flowers). Avoid anything that falls within the realm of somber and instead focuses on the celebration aspect of the gathering.
The outline for a celebration of life can be whatever you think the deceased would have most enjoyed - the key to any celebration of life service is to put together something akin to what the deceased might have pulled together prior to death. Invite the same people the deceased would have invited and host the celebration at a venue the deceased would have enjoyed. Play their favorite songs and serve foods they would have been glad to see served at a gathering.
Allow for plenty of time for guests to arrive and mingle. Make sure there are plenty of places to sit and have opportunities to have conversations; sharing memories together is one of the hallmarks of a good celebration of life service. You should set aside ample time for this informal gathering - for some people, the celebration of life service solely consists of this informal time of mingling and sharing stories in conversation.
If you plan on serving a sit-down meal, do so after you've allowed the guests to sufficiently mingle. Note that a celebration of life program doesn't always have to include a sit-down meal; some simply offer finger foods while others suggest a potluck which is completely appropriate. If a sit-down meal is in the plan, announce to guests to please find their seats for the meal. While it's fine to put out place-cards to give close family seats of honor, it's not necessary.
Toast to the Departed
Either during the meal - or toward the end of the event if there is no meal - the host should give a toast to the departed. You can then open the floor to other guests to share memories if you'd like, but it's important to keep this portion of the celebration celebratory. Save sad tears for the funeral or memorial service; the stories told here should attest to the life of the deceased and should compel guests to smile as they remember the deceased's life.
After the meal (or informal speeches), many people like to do some sort of activity to further celebrate the life of the deceased. Planting a tree together, having a bonfire, tying ribbons to a fence, or any other activity done as a group helps not only memorialize the deceased but helps guests in the processing of their grief. Note that many traditional celebrations of life activities (releasing of balloons, butterflies, or fire lanterns) have a potentially negative environmental impact and should be replaced by something else less detrimental to the environment.
Ending the Event
The conclusion of the celebration of life can be as simple as saying goodbye to everyone as they leave, but if you want something more formal, consider announcing a "last dance" to one of the deceased's favorite songs. Guests can either dance, sing along, or listen to the song reflectively. This moment marks the conclusion to the event, but you don't have to save music for the very end; you can play a mix of the deceased's favorite songs throughout the entire event if you choose.
A Customizable Experience
As long as the focus of the celebration of life program is in celebrating the life of the deceased, it can look like anything you want. A gathering at the beach, a weekend camping trip, meeting up at a bar, or ordering pizza at a friend's house can all work for a celebration of life program - as long as the people who loved the deceased are gathered and focus on celebrating the life of the deceased.