A running technique is the basis of any long-term program. Your arms should remain near waist level with relaxed hands and shoulders. Your posture should be upright. Focus on soft landings with your feet and try not to 'bounce'.
Work on proper stride form. Studies show that a toe-to-heel strike is better for running long distances than the heel-toe strike that used to be recommended. This technique can reduce shock in your ankles and knees and will lead to greater longevity in your running. When transitioning to a toe-heel strike, do so slowly and make sure you are doing post-running stretches.
Also don't forget to include strengthening and balance exercises into your training routine. These exercises prevent injuries and make running more comfortable.
But don't focus on your technique too much, there is no such thing as 'perfect' running form. You don't need to use more effort than necessary - just try to make your running relaxed and smooth. Give your body some time to create it's own comfortable running style.