I found this at another civ3 forum and I felt it pertained to us since we're playing the Spanish.
Since I quoted him I feel I should credit the source.
Gogf said:On the surface, Spain's Unique Unit, the Conquistador looks very weak. By the time they become available to you, you'll most likely have traded world maps with all Civilizations. If not, then an unarmed explorer will usually be fine, unless you're explorer a mass of territory with barbarians, which is highly unlikely, barring an extremely large map.
However, there is a golden hidden benefit to this unit that can only be utilized if you know how to use it correctly. By following a few simple steps, any AI you at at war with can be completely crippled:
1. Throughout your glorious conquests and wars, build an army. If you have already filled that army, build the military academy, and then another army. In this army, place one Conquistador.
2. You will not use this unit for combat, so there is no reason to pay extra shields to have a strong force in it.
3. This army will be all terrain is road, and will have three movement; meaning it can move nine tiles on land a turn, regarless of terrain. It will also be able to pillage without the loss of a movement point.
4. Move this army into enemy territory, and pillage away! You'll be able to pillage nine tiles a turn (including the one you start on), and be sitting on a fresh tile for the next turn.
5. Always protect your army with either a large stack of defensive unit, or an army of defensive units.
6. When pillaging, make sure to plan ahead. You want to come back in a circle each turn so that your one move defensive units (two move in the age of modern armours or if you are using an infantry or rifleman army) to be able to move onto your new square to protect your army.
7. Using this strategy, you'll be able to quickly and easily cut off each AI city from resources, cripple their production, and cut off all resources.
Since I quoted him I feel I should credit the source.