If using cold-eeze — "tropical orange" is the best flavor.
I have friends who have looked into this and think that zinc acetate is slightly better than gluconate and they take this one.
The procedure: when you first feel a cold coming on, suck on a lozenge and lie down/go to bed (and continue for another couple days).
This is not a supplement — the idea is that you want the zinc to coat the back of your throat, where the virus is replicating.
It’s most effective before the virus has had a chance to really up its numbers, so I'll sometimes take it preemptively if I find out I've been exposed to someone who was sick or if I've been traveling. Even if I do get sick, it’s usually mild. (I'm guessing because of lower viral load?)
Here's a meta-review of zinc lozenge use in shortening the duration of the common cold.