I started running over two years ago. So far I've done everything from 5ks to half-marathons. I've learned a lot of valuable lessons, some of them at my own expense. Below is a list of recommendations for every new runner.
Get proper footwear
This is a step you cannot afford to overlook. Buying bargain shoes is definitely tempting, especially when running shoes can be well over $100 a pair. This is one of the few times I'll say this phrase, "Spend the bucks!". The quality is worth it. Cheap shoes won't last as long and might not provide enough support or cushioning which can lead to injuries.
Along with this, I would encourage all new runners to get fitted for proper shoes. Many communities have running stores that provide this service free-of-charge. It's very simple. You'll be asked to jog on a treadmill for no more than 2 minutes. A specialist at the store will watch your feet and legs to see where your feet land, how they kick up, and any other nuances that indicate your style of running. Typically, they'll ask to see your feet as well (mostly to see what type of arches you have). From there, they'll bring out several shoes for you try out.
Buy your shoes one half size bigger than your dress shoes
If you buy your running shoes too tight, you'll jam your toes against the inside of the shoe while running. This can result in black toe nails. Black toe nails are relatively painless, but very unsightly. A blister forms underneath the nail, causing the nail to look black. In most cases, the nail will eventually fall off leaving you with a rather odd looking toe.
Invest in moisture wicking gear
Moisture wicking gear is not a must for any runner, this is merely a suggestion. I recommend it because the fabric is designed to wick moisture away from the body, keeping the body cooler during activity and allowing the garments to dry faster. Cotton and other fabrics tend to soak the moisture in and can be less comfortable on long runs. Having said this, I ran in cotton for months, at first, because it's what I already owned. I wasn't sure if I was going to like this "running thing" and didn't want to risk the investment. As soon I realized I wanted to run for years, I made the decision to go with better gear. I was still reluctant to spend a lot of money so I bargain shopped for moisture wicking clothes. I recommend paying attention to sales and hunting down bargains in department stores, most major stores carry moisture wicking workout gear.
Pay attention to your body
This is perhaps the most important advice on the list. Running, like all physical activities, takes a toll on your body. Some soreness and stiffness is to be expected at first, but don't allow a minor injury to turn into a major one. If you have persistent pains in your legs, knees, or back, you may be in the wrong shoes or your body may just need a break. Whatever the case, pay attention and listen to your body. Most of the time, it will tell you what it needs before a large problem arises. Do not be afraid to ask other runners, running store employees, or doctors about any aches or pains. Chances are, any runners you know are quite familiar with most of them.
Start Slow
So many times, new runners will dive right into a program and begin running mile after mile after mile. I'm not 100% against this, I just encourage new runners to start off with short runs a few times a week. Three or four mile runs 2-3 times a week is an excellent way to break into running. It's not horribly overwhelming and you'll have at least a day's break between each run to rest and allow your body to repair itself. You risk injury if you begin running and do multiple long runs per week. Build up to long runs slowly and give your body enough rest.
Eat Properly
Nutrition is key for runners. Give your body what it needs to perform it's best. Give it carbs, the good kinds. Go whole grain when you can, eat sweet potatoes instead of white potatoes, brown rice instead of white, and eat whole grain cereals instead of sugary cereals. Get plenty of vegetables and fruit and try to keep your meats lean. Your body is going to need a good bit of protein, I recommend fish because it has a lot of protein and Omega 3 fatty acids that are good for your body.
Plan Your Runs
You can spend a lot of money and get watches with built in GPS units, or you can plan your runs ahead of time using free services such as Google maps pedometer. I'm not against the fancy watches, they're quite useful. I would just put that purchase off until you're sure you'll be running for a long time. I recommend Google maps pedometer because it's a free service and fairly accurate. I use it still after two years of running.
Learn to Shrug Off Bad Runs
You've just come home from work and you're excited about your evening run. You ate spaghetti for lunch, drank plenty of water throughout the day and planned your route ahead of time. You switch clothes, do some stretches, and get ready for a great four mile run. Twenty minutes later you've only gone a mile and half and you feel exhausted. Your forced to walk back to your house feeling defeated. This is a bad run, and everyone has them. At some point, your body will be too tired, too stressed, or too bored to perform at an optimal level. Shrug it off. It happens. Even gold medal marathon runners have bad runs. Go home and relax, eat a nice dinner, and take a long, hot bath. You have the rest of your life to run, don't let this one discourage you.
Have Fun and Stick With It
No matter how much you love running, it will eventually seem like a chore. You will have a run that doesn't go well, you will get sore, you will be passed by 70 year olds from time to time. It happens, and it's all happened to me. Running takes self-discipline and self-motivation. You'll rarely find a running cheerleader. Most people will tell you you're crazy for spending your free time running. Ignore them. Running is challenging and exciting. So go for it!