Lots of threads on this. Equalizing gently before descent is a good tip. So is swallowing, or tilting your head from side to side, or breathing out through your nose, do a feet first vertical descent, descend slowly, or all of the above. Also, don't over think it. Don't equalize "too hard." Don't obsess. The more you re in the water, the more you will be used to the feel of water on/in your outer ear. Even divers with thousands of dives have the occasion where clearing is not as easy as they are used to, me included. Take it slow, and all will be well.
DivemasterDennis