I've noticed that there are alot of people who are using single-player maps, that're having problems with dropships in-game (Not the dropship loadout, but say getting reinforcements from off the map using a dropship trigger). Here is how you do it:

Set the taskforce (Make sure the Dropship is first in the list)

1 Dropship
2 Titans
2 Wolverines

Then set the event (Most important part for a dropship trigger)

1 Move to waypoint XX (This will be the waypoint where the dropship enters the map)
2 Unload (Select the option that says keep transport, loose units)
3 Move to waypoint XX (This will be the waypoint where the dropship leaves the map)

Then create the new team type.

Waypoint = X (Where it'll be appearing from off the map)
TaskForce = The Dropship Taskforce
Script = The Dropship script
AutoCreate = Check
Full = Check
Owner = Make sure it's the correct owner (More than likely GDI)

Now set the trigger.

Basics:
Repeat = No
Disabled = No
Attatched Trigger = None

Events:
Elapsed time = (Whenever you want it to arrive, set to 0 if it's right at the start of the map)

Action:
Creat Reinforcements at waypoint = Select the dropship Team type, and the waypoint of where it'll be appearing from.

In-game, your dropship will arrive, drop off the loaded units, and then the dropship will leave the map.
You now have a sucsessful dropship trigger. This'll be useful for those who want to make some GDI single-player maps.