It would be a good idea to take a look at the route you use in training and make a note of the relative grades you use throughout your course. Perhaps take the time to walk or drive along the entire route, and write down the information of how much of the route grade is up, how much down, and how significant the pitch is on the side you usually run.
Other than looking for flatter courses, runners should look for overall balance in the surfaces they run on. If part of your course pitches right or left, try to work in a return trip down the same bit of road, but heading the opposite direction, so that you’ll shift the extra stress off of one foot and leg and onto the other. Uneven surfaces produce injuries because they lead runners to develop unbalanced musculature – your leg (especially the calf and shin) responds to the strain of graded surface by bulking up certain muscles a bit. If complementary muscles don’t bulk up to the same degree, the imbalance of muscles brings on injury. To stay healthy a runner needs to balance out the surfaces on their training course. As you do that you will help complementary muscles balance out as well. The muscles that you build going uphill tend to balance the muscles you build when you run downhill. If you do find yourself with an injury, be sure to get help and treatment as soon as possible and check your training route!
If you have a terrific place to run that doesn’t lend itself to being part of a balanced course, you may make the changes necessary by keeping the distance you run on a grade (slant) equal by staying on the same side of the road both out and back. The grade would be on one side of your body on the way out and on the opposite side on your return, thus providing balance to your legs.
If you have a course that is not an out and back route then you need to adjust by switching from one side of the road to the other in an attempt to create balance in your leg muscles. For trail runners you should alternate your trail route if you do not have the ability to balance out the slant, or grade of the course. The key is balance.