First than anything, check if is water or coolant in the radiator, also check if the fan are turning on, try with AC on, they should start spinning immediately, also with the AC off after the engine have heated up a bit. You could also try (with the engine running) to check visually if there is any leak of coolant by the hose, be careful of touching cuz can be really hot.
Most of the time is one of the first two.