This is not medical advice; I am not a doctor and I have no medical training.
http://www.nhs.uk/Planners/birthtofive/Pages/Childhoodillnesses.aspx
They often follow a cold and sometimes cause a temperature. A child may pull or rub at an ear, but babies can’t always tell where pain is coming from and may just cry and seem uncomfortable.
If your child has earache but is otherwise well, give them paracetamol or ibuprofen for 12-24 hours. Don’t put any oil, eardrops or cotton buds into your child’s ear unless your GP advises you to do so. Most ear infections are caused by viruses, which can’t be treated with antibiotics. They will just get better by themselves.
Sometimes people do not recognise that a child has an ear infection.
http://www.nhs.uk/conditions/Otitis-media/Pages/Introduction.aspx
Chronic otitis media is a middle ear infection that lasts for a long time or keeps coming back. As the symptoms are often less severe than those of an acute infection, the infection may go unnoticed and untreated for a long time. This may cause more damage than an acute infection.
Here's a technical list for diagnosing symptoms:
http://www.cks.nhs.uk/otitis_media_acute/evidence/supporting_evidence/diagnosing_acute_otitis_media
Limited evidence from a systematic review suggests that the most accurate individual symptoms and signs for diagnosing acute otitis media (AOM) are ear pain, ear rubbing, a cloudy or distinctly red or bulging tympanic membrane, or a distinctly immobile tympanic membrane (on pneumatic otoscopy). Fever, upper respiratory tract symptoms, crying, restless sleep, and irritability are individually less useful, but no studies have assessed the accuracy of several symptoms and signs combined. These findings are limited by bias in the studies included in the review.