Soft structured baby carrier or structured hiking backpack
fanny pack or pocket for keys, phone, etc.
Layered clothes appropriate for weather
Hats for you and baby
Sunscreen
Water bottle or Camelbak type bladder (Tip: Get baby used to drinking out of a Camelbak so that he/she can use your water)
Snacks
Light blanket or scarf - for shading baby (Tip: Wrap a scarf around backpack's top handlebar to help stabilize pack on a slope)
TP
Diapers; wipes; small bag for trash
Extras - First Aid kit, sunscreen, sunglasses, power yummies, pouches, infant insert for small babies; small towel to wipe dirt, (After hike: Bumbo seat, mats/picnic blanket, bamboo cutlery)