Tx eustachian tube. More than likely your eustachian tubes are not doing their job to equalize the pressure in your ears. Use an oral decongestant or oxymetazoline nasal spray as directed. Then you can pinch your nostrils shut and gently/carefully blow your nose. You should feel a little pressure change in your ears but it may not clear initially. If it persists, see an ENT (otolaryngologist).
Valsalva. Pinch your nose, close your mouth, and then try to blow your nose. This will help unclog your ears. You can also swallow, chew gum, yawn. You can take sedated or afrin (oxymetazoline) before your flight (assuming you do not have any medical contraindications to these medications) to help as well.