Is there any good way to prevent my knees from hurting while running? no significant injuries, but running on trails or pavements causes pain.

Running pain: There is no magic answer. Issues to think about include: (1) high-quality running shoes; (2) level surfaces (beware of running on surfaces with even a little incline to either side); (3) run on soft surfaces (flat dirt path or turf or soft running track are best); (4) have an consultation with either a professional trainer or a sports medicine doctor to analyze your stride, strike points, etc.

Runner's knee: Sounds like runner's knee. Try obtaining a cho pat band that can be worn over the mid portion of your patellar tendon halfway between the bottom of your kneecap (patella) and its insertion on the proximal tibia. Ensure that your hamstrings and quads have good eccentric strength and are well stretched and consider orthotics in your running shoes.