From Warrior I...
a.) put arms forward
b.) move your bag leg in closer a bit while bending your front leg
c.) kick back leg up
d.) straighten your back leg so that from the tip of your foot to the tips of your fingers is straight in in alignment.
e.) remember to breathe!
The benefits of this pose are great, if the pose is done right. Like almost all poses in yoga, it clears the mind of outside distractions. It quiets the mind and reduces anxiety. This helps when you go back to your normal day routine because you are less stressed and irritated. Also like most yoga poses, it helps with your balance. We could all use a little better balance in our lives, I know I sure could. It helps so that you dont trip over things as much which is always a good thing! Going back to the less stressed, it helps calm the nervous system. This makes you less likely to lash out or snap. It also apparently helps with your digestive system says one source. Everyone likes it when it flows easier! Not to be gross or anything but that definitely would make a lot of people's day better.
Overall, many things make this pose a very good one to use during practice. It fits in almost anywhere in your yoga schedule. Helps clear the mind and give you a calmness, gives you better balance and helps your digestive system. So get to working on Warrior III!