What clothes do I need?

This is the list of clothing that I have used (from late May to mid October):

At the time of my writing this post I just climbed Mt Whitney on Memorial Day weekend (May 25, 2013) and below is the exact clothes I wore: 

Footwear

ASIC Mens Gel-Trail Attack 7 Trail Running Shoe ($60 USD)
They are light weight and give your feet more mobility. However, if you have a heavy backpack, they do not absorb the weight very much and it can hurt your knees. More on backpacks later. 

Socks

I only use smart-wool socks. You can get them at REI or any other major sporting goods store. They are great because they do not absorb moisture and they keep your feet dry. Very important when hiking. They also keep your feet warm at night because they help retain heat. Range from $10-20.

Underwear

Again, smart-wool is the best for underwear ($50-100). Keeps you dry and it's easy to layer over it. If you cannot or do not want to get smart wool, you can buy under armor type underwear. I've used that before on my hiking trips and it works just fine. Does hold some sweat so it can get cold when you're not moving. I got them at Target for about $15.

Pants/Shorts

I use REI's Sahara Convertible Pants with No-Sit Zips ($65). They are great because you can zip it off from the knee down and they become shorts. And if it gets cold, you can easily zip the bottom back on. They are lightweight, easy to pack away, and dry fast. 

Take a warm pair of pants to sleep in. REI Polartec 100 Teton Fleece Pants ($60)

Shirts

You want a base-layer that does not absorb your sweat. Smartwool is the best. But I have used running shirts from Target that cost me about $15-20. You will have to layer up over this base layer but more on that later.

Jackets

You want two of them:

1. Mid-layer: something that will act as a warm liner such as fleece. 

2. Outer-Shell: something that is waterproof and breathable that will protect you from the elements (rain, wind, etc)

I use Columbia Men's Bugaboo Interchange Jacket. ($190). It has two jackets in one and you can attach them via zipper. It comes in very handy when it's cold, and if your're too warm, you can just use one of the jackets.

Take one pair of each item above (except shoes) for each day you will be hiking. Unless you just want to be really lightweight and use the same clothes again the next day.