Higgins is right, you need far more edge loops, especially in major joints, to give this character a chance to deform correctly. In games nowadays, even the most insignificant characters have a much higher polygon budget than you've allotted for this character. Take a look at this model, notice the good use of polygons, how they are distributed to areas where deformation will be heavy (elbows, knees etc...) also, notice how a strong texture can make even the simplest model look awesome!!
Keep it up, dont stop modeling, every model you make you learn something new!
Windows XP Pro x64 - ASUS P35 Platinum Mobo - nVidia GeForce 8800GTS 640MB GPU - Intel Core2 Duo E6750 @ 2.66GHz - 4GB DDR2 1066MHz RAM - Two Hanns-G HW194D Displays @ Duelview Configuration