Run at a comfortable pace, easy enough that you can hold a conversation. If you're huffing and puffing, you're going too fast. Don't worry about your speed. Just focus on covering the distance.
When you're running uphill, don't try to charge up it; you'll spend all your energy by the time you get to the top. Try to run relaxed. Keep your hands loose, and keep your shoulders away from your ears. Just think of letting the road rise to meet you.
Be sure to sandwich each run with a warmup and cooldown of 5 to 10 minutes of walking and easy jogging, even on days that call for short, easy runs. Doing so will help you feel more comfortable on the run and will help prevent injuries such as muscle pulls.
Today is your long, slow distance (LSD) run. The long run is the backbone of any successful training program. It builds your aerobic base, increases your endurance, boosts confidence, and helps you rehearse some of the gear and fuel strategies you'll need for the race. It also helps you prepare for the psychological challenge of racing for a few hours. Since you'll be running farther, you can go out slower than you usually do. On these days your goal is just to complete the distance feeling good.
The purpose of easy days is to develop the endurance, strength, and cardiovascular fitness you'll need for the race. You don't want to take them so fast that you're sore the next day. At the end of the run, you want to feel like you have the energy to run longer.
If you don't have hills where you live, you can improvise. Bridges, parking garages, and steps can all provide substitutes for hills if the area where you live is pancake flat. Just watch your step--and look out for traffic!
Next week, you're going to be attempting your first race-pace miles. So it's a good idea to get a sense of what a realistic race pace and finishing time will be. Just plug a recent race time into the training calculator at runnersworld.com/trainingcalculator. If you haven't run recently, you can do a 1-mile time trial. Go to a track or a flat, 1-mile stretch of road. After a warmup, run 1 mile at a fast effort, and note your time. Run 1 mile to cool down. Plug that time into a training calculator to get an estimate of your finishing time for the half marathon. Also, look at the training paces to figure out what your easy training pace should be.