What are the advices to travel well?

The watchword: choose comfortable clothes to feel at ease. You will need to lean on comfort rather than elegance: loose clothing and comfortable shoes will be required.
If you are lucky enough to go to a sunny spot during winter, please do not forget that you will need to come back with warm clothes. 

Toiletry bags (without sharp or pointed objects, or products which contains more than 100 ml of liquid) are allowed. Keep elements to refresh yourself handy, brush your teeth... Skin may also suffer from discomfort during a flight: do not hesitate to moisturize it often with a proper moisturizing cream. 
Sleep well before departure and don’t fast (favor a light diet by restricting stimulants): two principles to begin your flight peacefully. 

If you suffer from circulatory issues, consult your doctor before the flight, who shall prescribe preventive treatment, if need be. During the flight, remember to get up regularly and walk a few steps, this gets the blood circulation going and relaxes the legs.
Take the opportunity to stretch. Even while you’re sitting down, you can also do a few small ankle and leg movements.

On take off, change in cabin pressure can cause some ear pain. The best way is to unwind by chewing gum for example, swallowing small sips of water, or by yawning. For a baby, plan a bottle of water or fruit juice, to make him drink gradually, throughout the takeoff.
The air conditioning from the air taken at high altitude is very dry, and the cabin atmosphere is affected. Lean on hydration! Drink plenty of fluids to keep your body hydrated.
Avoid drinking too many carbonated or sweet drinks and prefer water: do not hesitate to ask for a glass of water from our on-board staff.

Careful with alcohol as it dehydrates and its effects increase with altitude, even in a pressurized cabin.