Bring a light, collapsible pram/stroller. If you have an infant bring a baby carrier (I found Ergo Baby the best) so that you have your hands free and your child stays close.
Prepare for air pressure and sickness - Bring a sippy cup, lollipop, chewing gum or be ready to breastfeed on take-off and landing, depending on the age of your child. Sucking will help with the ear pressure for your child. Also, bring pain relief (Panadol) for emergencies.
Be a Smart Packer- Pack a bag that has everything you need, and you can access it quickly. Bring as much as you can fit in the carry-on. Don't forget to pack enough nappies (about 1 an hour is recommended). Bring lots of healthy snacks. Don't forget their comfort item (dummy, favourite toy). Bring lots of dummies in case they fall on the floor. You will need to distract your child for hours, so bring drawing items, iPad or device with their favourite shows already uploaded, books and child-size headphones. Lastly, plastic bags, wet wipes and hand sterilizer are a must.
Plan the Clothing Carefully - Dress your child in layers, so it is easy to change them when the temperature changes. Choose clothes without buttons, zippers, or anything that could prevent them from getting to the bathroom in time. The same principle applies to shoes: Avoid laces. Also, don't forget to bring a change of clothing in your carry- on.
Plan for Hunger- Take as much food as you can fit into your carry-on luggage for toddler air travel. Don't count on being served any meals in the air since many airlines no longer offer food. Even if your flight isn't scheduled to be in the air during a mealtime, plan ahead for delays, and bring easy to eat food (cut-up vegetables, string cheese, small bags of crackers or granola bars).