My 1993 ford f-150 truck will not start when cold, but starts when warmed up.

Many cold weather starting problems with older cars/trucks are related to high mileage issues or specifically low compression. Of course there are probably dozens of other causes ... but you asked a general question

Because if you look at the engine temp dial when it's down the truck/car will start meaning the engine is cold and also it may be because some people not meaning you do but some people leave their vehicles sit outside all season long.