Toyota Repair: 1985 Toyota MR2 Overheated, toyota mr2, headgasket

Question
I just bought this MR2 and I love it however it overheated in the city.  We put water in it and checked for leaks while it was parked.  I think I notice a puddle under the passenger side. But it rained and am not sure if it was the car or the rain.  What could cause it to overheat? What do I need to do to fix it?

Answer
Overheating can be caused by many things.
The thermostst could be stuck closed or partially closed.
There could be an external leak from a number of places,
A leaking hose, water pump or radiator, the best way to diagnose this to to pressurize the cooling system to see where the leak is.
The cooling fans in the front may not be working, they should turn on when the engine reaches operating temperature.
Wost case scenario would be a leaking headgasket in which the cylinder head would have to be removed.
Any decent repair shop should be able to diagnose this.