Clothing needs to be selected to fit the weather. (Hot Summer or cool / cold spring or fall weather)
We suggest that you dress in layers. By dressing in layers you can adjust your clothing to stay comfortable throughout the trip. When assembling your clothing for a trip, think about the various combinations you might use in different weather conditions: From hot to very cold. From dry to wet. No wind or high winds. In the Spring or fall it can be warm and sunny when you start up the mountain, and snowing when you get to the top.
 I am a medium size guy but I have a few large / extra large garments that fit over everything else while sitting or standing around.
 Remember that you will sweat while hiking and need breathable clothing to get rid of the moisture. Modern synthetic materials are quick drying and breathable. In eastern North America you will encounter rainy days on the trail. Leave your cotton jeans at home.

You will not take everything on the list all the time (two hour hike), and you may add to it.
 If you are hiking with a group of people, equipment can be shared. One person carries the stove and someone else carries the water filter. Divide the weight up equally between hikers of equal ability.
 Most of your gear needs regular maintenance. Make sure that your stove is working, before heading out to the wilderness.

Day Hikes

Day pack
Flashlight or  Headlamp  (Petzl Tikka)   Longer trips bring extra batteries.
Compass,   preferably with luminous markings for use at night. (Such as a Sunto MC1 or A30)
Maps
Fire starter  (lighter, match safe, or any emergency fire starter that works)
Knife, Watch
Water bottles or Camelbak
Insect repellent , Sunscreen, toilet paper
Personal medications if needed.
First Aid Kit, Whistle
Hat, Cap, Head wear ; Gloves or mittens.
Rain Gear (jacket and pants) A Gore-tex rain jacket can also be used for your wind shell.
Wind jacket if rain gear is not breathable.
A warm fleece, vest, or quilted middle layer. (A lightweight quilted jacket with hood is good in cool weather)    
Light quick-drying trousers or hiking shorts, Belt.
A quick drying shirt.
 (long sleeve shirt and pants are good protection from Black flies, and to much sun, sunburn.)
Hiking boots and socks.
Extra Socks in waterproof bag.
Long underwear (poly or wool)
Food
Water
Extras:
Camera, Binoculars
A Walking stick or Trekking Poles are necessary when you have to wade across streams and small rivers.

Boots should be well broken in and comfortable. Waterproof (Gore-tex) boots are good in the eastern states.
Gaiters are sometimes good when wearing low cut boots or shoes.
I usually like the lightest boots that I can find. But remember that you need more support (good arch support, stronger soles) when backpacking with a heavy pack, than on a day hike carrying little weight.
When you go to the store to try on boots get a boot that fits well. Also think about how much the boots weigh.
Get good moisture wicking socks.
Find out what works best for you, while hiking around home, before your wilderness trip.

Additional gear for backpacking and overnight trips.

Larger Pack
Sleeping Bag in waterproof stuff sack and sleeping pad.
Extra clothes in waterproof stuff sack
Tent , ground cloth
Stove and fuel
Cooking Pots and utensils  (cooking Kit).
Water Filter
Food Bag and rope, to hang food in tree away from Bears.
Personal Gear:  Toothbrush, comb, razor, soap, etc.
 You will need a good lightweight mummy sleeping bag.

For use in the early spring and fall you want a bag that is comfortable when the temperature is down to freezing. {32F}. The weather may be warmer, but we do have frost  in the mountains during early and late season. Look for a bag that is warm and lightweight. Around 2 or 3lbs total weight.
 Sleeping Bags for summer camping do not have to be as warm and can weigh less.
Price varies, But could be $200 or less. Marmot and Mountain Hardware make good backpacking bags. So do quite a few other manufacturers.
 Get good boots that fit well.
 Get good breathable rain gear. When you are on the trail for days at a time you need good quality rain gear.
 Think about weight for everything you buy or put in your pack. Google lightweight hiking or Backpacking. See what others are saying about the gear that is currently available. Technology is constantly changing and we never know when a significant improvement will come along.
Also think about what you can leave out.
 There is quite a difference in the weight of modern backpacks. And it does not have to be the most expensive to be lightweight.
 I do like a light waist belt on my backpacking packs. The belt puts some of the load on the hips and takes some weight off the shoulders. Don't get carried away with this though. Some belts / suspension systems are to heavy.
I like a pack that is just big enough for the necessary items. I do have some older packs that are to big and too heavy. They stay home.