Enkhidu said:the players putting up folder paper signs in front of them with the spell/effect, making sure that if something new goes up or comes down they let everyone know.
We do that, although I have the players hang the signs on my DM screen, so they're easily visible to all (and the Prayer sign has a "DM's side", since it has a negative effect on the bad guys). In most cases, the effects last the entire combat, so I don't worry much about what expires (and thus would get taken down), but if there's something that does (like bardic music), I'd put a tick mark with a pencil on the sign each round, on the appropriate player's turn.