I was giving some advice today to a colleague about an "occasional service" -- it doesn't matter which kind -- and remembered one of my bugbears: having enough people in the service to make it go smoothly.
Ministers or lay worship planners -- so I gather -- often talk about distributing responsibilities to include more laypersons in worship, but it's been my experience visiting churches that this gets translated into reading lections and taking up a collection. Or, it is manifested as more responsive readings or other speaking roles for the people in the pews. Some, of course do it well; this is intended for those who don't yet. And this is one area where large churches, perhaps out of necessity, have the advantage.
So: how many of us have been in worship where too few people have fumbled liturgical actions that would have been made perfect with more people. Anything with a hand-held microphones or paper certificates (or flower or other tokens to share) come to mind: an assistant to hold (or pass around) one and distribute the other make a neater presentation. The alternative is the worship leader trying to hold too many thing, or awkward communications to move the the next liturgical step.
Where candles are used, ushers can make lighting candles safer and pass off a taper used to light the candles. In membership induction services, special honors can be given to poor speakers by giving them the role of formally welcoming the new member by shaking hands or sponsoring them, if these roles aren't already filled.
Equipment for worship -- I'm thinking here specifically for communion or baptism, but the idea is widely applicable -- needs to be tended, set up, used and removed or replaced. There are opportunities for learning and trust that can give members of a congregation a low-risk, low-commitment way to serve, provide there's the imagination and a plan to provide for it.