How to prevent ear infection?

I guess, since ear is a little complex than other body parts where you cannot look inside and wouldn't know anything until it aches one day, so I suggest regular check up with an ENT doctor would be the safest bet. Little things that we can do is, after bath make sure you dry the water off the ear, and keep the outer ear clean.

Try not to share toys, put things in mouth or ears. Limit pacifiers recent studies shown that it may increase chances of ear infection. Limit it to bed time. Keeping up to date with all vaccines. Basic steps for us to manage on our own. Hope this helps.

A regular visit to the ent will definitely help. My kids aged 6 and 7 go on a quarterly basis for ear cleaning.