In the past 7 months I've gone from hating running to being a runner, from running 6 miles straight for the first time in my life to running a 43:22 10k, from running 5-10 miles a week to 40+. Here are the most important things I've learned.
Improve your cadence
Your feet should hit the ground this often, even if you are going slow. This is the single easiest and most valuable improvement you can make to all aspects of your running. This might not feel natural at first, so you have to be intentional about it.
Build a base of easy weekly miles and run slow
If you're starting out totally untrained, some sort of alternating running/walking program is the best way to start. C25K seems to be the most popular one.