In my parish we usually use a few that appear in the missalette we use. The last one is always for our own personal intentions with a moment of silence to allow us to silently offer those requests to God.
When I was the secretary it was my responsibility to prepare them, now a volunteer does that. Since our parish includes a military base with no Catholic chaplain making us their Catholic Parish, I always added one for the military, chosen from a selection provided by the Military Ordinariate.