What is the effect of price controls on buyers and sellers?

Assuming you mean an actual price control, such as a ceiling or floor, there are two very easily-identifiable effects.

When thinking about price controls, think of the supply and demand curves and remember that with a price control, it is impossible for a price to get into equilibrium. With that in mind, we can identify two problems that result from this.

1. A shortage/oversupply of the good. If there is a price ceiling, you have a shortage (a la gasoline during the price controls of the 70's.) If there is a floor, you have overproduction (a la ethanol. Which, granted, is subsidized, but that is effectively like a price floor).

2. An inefficient allocation of resources. With ethanol being subsidized, we witnessed a massive increase in the price of corn. The market did not want this, and thus we saw an inefficient allocation of resources.