Weekly speedwork should be between 5 and 10-percent of your weekly mileage. For example if you are running 25 miles per week, you should not exceed 2.5 miles of speedwork. When using this formula, factor in all high intensity runs for the week as speedwork.
Don't over do it! This is the classic mistake made by most new runners. Stick to a progressive schedule, even if it seems a bit easy at first.
Find a running partner. Running is easier when done with a friend.
Use your days off wisely. These days are meant for recovery, therefore it is important to spread them out. If your schedule calls for two off days, don't take them on consecutive days -- spread them out.
Stretching is important, but never stretch cold muscles. Before you begin your stretching routine jog lightly to warm-up your muscles.