Here are excerpts from an equipment list I made for a backpacking class. This list was intended to give folks a basic idea of the items needed for a spring to fall backcountry trip. Whether the trip is an overnight or a six-month journey the list remains basically the same. This is not a bug out bag list, though my BOB contains most all of these items. My BOB serves the dual purpose of a get me home bag and a stay out for a little while if I have to bag.
When thruhiking the goal is to carry as little weight as possible while still having what you need to be safe and comfortable. The latest thing in thruhiking is the ultralight craze. You carry so little that you are only comfortable when moving. If lost or injured and forced to stay still for awhile, ultralighters end up very uncomfortable. As with most things in life it is about balance.
One suggestion I will strongly make is to carry the lightest gear possible that will still do its job and hold up for a reasonable amount of time. It is up to you to decide which gear is right for your journey. But, the goal should be for your pack with food and water to weigh less than 1/3 of your body weight (closer to 1/4 is ideal).
Backpack - internal or external, generally between 4000 and 6000 cubic inches
Sleeping bag - down or synthetic usually rated between 15 to 25 degrees
Sleeping pad – self inflating air mattress or foam pad
Shelter - tent, bivy or tarp. Less than 4 lbs. of shelter weight per person is ideal.
Make sure you get the pack professionally fit. Most folks at outdoor gear stores do not know how to properly fit a pack. A comfortable pack will make a heavy load more bearable. A poorly fitting pack will make even light loads painful to carry. Look for someone who truly knows what they are doing. A good pack fitter will insist that you put a full load of weights in the pack and tell you to walk around the store for awhile to see how it really feels.