A lot of divers have problem with their ears not equalizing and hurting when they go diving.
Dr Edmund Kay - an ear and nose specialist and diver for over 20 years - discusses the problem and the different ways to overcome it. He also warns why trying to equalize, when you're below 10m - by vigorously blowing your nose, is a bad idea.
See the video here:
A bit from the site:
For individuals who have difficulty pressurizing ears, the position in the water column is extremely important. It is well known that the head-down position during descent can make middle ear equalization more difficult. Less well understood is the reason for this effect. There are soft tissues in the nasopharynx which surround the membranous Eustachian Tube, and no doubt gravity plays a role in there normal functioning. The most likely candidate for positional obstruction is this soft tissue. A sub-optimal position can compromise marginally patent Eustachian Tube. For this reason it is advisable for students to begin descent slowly, and always in the head up position. Divers with prior ear problems, timid divers and those who are not sure whether middle ears will equalize should also assume this position. Half of the Eustachian Tube is surrounded by bone but the other half is open to the pressure changes of the respiratory system (ambient pressure). This membranous later half is partially surrounded by a "C" shaped cartilage and during swallowing, muscles of the soft palate pull on the Eustachian Tube. This traction opens the tube while closing the nasopharynx. The act of swallowing often causes a clicking or crackling sound to be heard and this sound is the noise made when the moist tissues of the Eustachian Tube pop open. You can hear this sound for yourself in a fellow diver or student by applying a stethoscope in the area around the ear. If the student swallows and the crackling sound is heard, the listener can verify that the Eustachian tube has opened. This technique was first described by Joseph Toynbee in the 1800's, and will be described later.
Thanks to Bianca for listing this video on her site!! Thanks Bianca!!