
Pumping Iron
My arms are not big, but...
Just a brief guide:
Any form of weight exercise when you are older serves to only increase the density of your bones, and very very little on the thickness. Thickness is either due to frequent exercising when younger or due to genes.
If you mean bigger muscles, then yes, weightlifting do help. However, please bear in mind that weightlifting only trains one aspect of your body; fitness and health are not just lifting weights alone. It is a combination of many other factors, one of which includes cardio.
For me, I believe not only in weight training, but other forms of locomotion like jogging and swimming. =D I don't like jogging, but I still jog because of the benefits it gives and because I need to maintain for my IPPT. I like swimming though; it gives you the power of being able to move in another medium.