So here is some advice from a runner who's made every mistake in the book.
1. Never run an unfamiliar course without driving it first. I'm so bad about doing this. I have GPS on my phone, so why not run an unfamiliar road? I like a little adventure, seeing new sights, etc. so what's the big deal? A) Hills. It's really really good to know how hilly the course is before you try it out. Yeah, you'll survive even if you're unaware, but it's just better to have the heads up. Trust me. B) DOGS. In my neighborhood there are dogs everywhere! Most of them are chained up or in a pen, but you can't rely on this! Drive your course before you run it and look for dogs or any signs of them. And, to be extra safe, run with some pepper spray (just in case!).
2. Run on the left side of the road. I am so grateful that someone once upon a time gave me this advice! It seemed dumb at the time. Why would I run on the left side of the road when you're supposed to drive on the right side? Is that even legal!? Where I run there are no sidewalks and no shoulders, only a road and a ditch. If you're running on the left side of the road you're able to see the cars coming towards you. If you're on the right side... you're blind to the traffic coming up directly behind you. People don't always pay attention. They're texting, talking on the phone, looking at their Garmin, or (if they're anything like me) they're distracted by the two year old throwing cheerios at them from the backseat. If you can see those drivers coming, you can jump into a ditch if you need. If you don't see them, and they don't see you... Ouch.
3. Always warm-up before you run. Again, I'm so bad about this. I'd rather just take off and get it all over with, but that's bad. That's the kind of thing that leads to injury. A good warm up will get your blood flowing and your heart pumping, and that leads to better performance overall. A good warm-up depends on how far you're running or even how much you'll be pushing yourself. For me, I usually go anywhere from 2-6 miles and I don't push myself much, so a decent warm-up is usually an easy 5-10 minute jog and some minor stretching. Read more about warm-ups here.
4. Drink plenty of water. You know it, I know it, everybody knows it: water is GOOD for you. Personally, I'd rather fill my body with coffee and Dr Pepper, but those things kinda suck for a runner. I can always tell on days that I haven't had enough water: my muscles are weak and I get tired very early in my run. Muscle fatigue, my friends, is no bueno. You should be drinking water consistently all day long. If you're thirsty, you're already dehydrated. More on the benefits of drinking agua here.
5. Never run in your [pretty] new running shoes without breaking them in first. Have I ever done this? You guessed it: Yes I have. I bought these gorgeous Under Armour shoes and was SO excited when they arrived in the mail. Aside from the mistake of buying running shoes without trying them on first, I decided to run in them that same day. The sad thing is I knew I wasn't supposed to do it. Six miles later I had a quarter sized blister ON MY ARCH. Not to mention the fact that they were the most uncomfortable pair I'd ever put on, much less ran in. When you buy new shoes it's important to wear them and let them conform to your feet. Sometimes they will inevitably cause blisters, but I've learned that, after I've worn them several times and gotten used to the way they fit, the blisters go away and never come back.
6. Always do some kind of cool down after you're finished. This is one thing I definitely can't skip. A warm-up help your body to go from a resting state to an active one, and a cool-down does just the opposite. It's not good to just stop all at once without giving your body time to go back into chill mode. When you've finished your run, try to jog or walk for a while, 5-10 minutes. Let your breathing become more even and your heart rate go back to normal. I can usually tell when my body is cooled down because the flow of sweat begins to subside! Now is also a good time to stretch. If I don't do these things, I get muscle cramps like nobody's business.
7. Practice breathing correctly. Did you know there's a wrong way to breath? Crazy! Most people breath with only the top half of their lungs. When you breath you shouldn't just see it (or feel it) in your chest--it should go all the way down into your stomach. This is actually hard work, I tell ya. I have to practice breathing on a regular basis so that I don't have to think about it as much during a run. Try it for a sec: Take a deep breath and expand your lungs all the way down into your belly button. Your stomach should expand. I've learned that breathing correctly not only fights fatigue, but it also helps with side stitches. I used to get them so bad that I would have to stop running altogether. But now that I breath correctly I can literally get rid of a side stitch as soon as I feel one coming on because it utilizes the diaphragm. More info on this here.
I'm no expert, and I would never pretend to know everything there is to know about running (although my husband would probably disagree with that statement), but these are just a few things I would recommend ANY runner to at least consider and even do some research on.