Brehs, before going on a running stuff, take a look online and learn about strides and above all about your walking type.
Some run on the outside of their feet, so on the inside and the other are intermediate. Knowing that will help you find the proper shoes and avoid injuries. Also, if you're a beginner, start slowly and by doing split runs, it will reduce the potential injuries on your beginner's legs. Also learn to land between the mid-foot and the heel in order to get the most efficient stride and start on good basis. The more you start well, the less you're prone to bad habits and the less you'll be hit by injuries.
Myself last year, I wanted to prep for '13 Paris Marathon (began in August, aiming for April) and even if my cardio was a+, my legs didn't follow. I experienced pain in the outside of my knees around late September, probably due to the wrong shoes (which was weird because I documented myself before choosing them but still) and a way too hard schedule. I stopped jogging and started riding my bycicle instead and still now I have knee problems sometimes when I play football with my brehs (increased by my snowboarding accident last year), so take it easy and increase your distances progressively and reasonably. Don't rush stuff.