Here are a few random thoughts about hiking in Corsica. This is not an introduction to hiking! only a few notes concerning some extra precautions to take in Corsica.
Beware of pigs at night. You should hang your backpacks up in some tree, otherwise they'll smell the food inside and tear through your bag to eat it. There are places without pigs, but it's hard to tell, so stay on the safe side. Many shepherd's huts have sheepfolds where you'll be safe.
Get up early. The best thing to do is to wake up before the sun, pack everything up, and get going at sunrise, near 6 o'clock. This lets you appreciate the cool morning air. It usually gets really hot as early as 9 o'clock. The hottest time of the day, around 2, should be dedicated to a siesta, unless you're in a real hurry.
Carry a large flask. 1.5 liter sounds right. 1 liter should do but you might be in trouble if you don't find a spring before the evening.
No special equipment is needed, just the usual mountain clothes. Remember that although the wheather is usually hot and clear, you might also experience a few violent storms.
You should carry an "Aspivenin", a small device used to pump the poison out after being bitten or stung by a venomous animal. As far as I know, there are no vipers in Corsica, but there are small scorpions...