Getting better in the kitchen
I'm sure there are a million ways to do this, so my answer isn't "right", it's just how I've learned. 

Get a good cookbook and follow recipes from it. Ideally, you want a cookbook that discusses the "why" as well as the "how". I highly recommend The Best Recipe for this. They have detailed explanations of how they created the recipe and why certain things work. Having a good understanding of why will allow you to really understand the steps of a recipe, making it easier to improvise. 

Look for some courses. If you live near a major metro area, there is almost certainly somewhere to take some cooking courses for the home chef. Look for some 101 level courses. Our local cooking school / gadget shop / place I spend too much money is Cooks Warehouse. They have classes like Knife Skills, Pasta 101, Summer Veggies, Intro to Cheese Making, BBQ, etc. Take a class or two. 

Ask and research questions here. If you want to know "how to..." there's a good chance that there's already a good question on this site. Reading about steak for instance, you'll learn a TON, or look for Beginner Cooks. Do your research. If you don't find your question, ask away. There's no question at all that I've become a better cook because of this site. 

Find someone to cook with. My wife could cook pretty well, and I learned a lot from her. Later we made some friends and gained a neighbor who were professional chefs. Cooking in a kitchen with them, even if it's just helping, can be very helpful. You'll learn a ton. Don't be afraid to ask questions. 

Cook the same dish over and over. Find a dish you like and make it a couple of times from the same recipe. Then look it up online and look for some recipes that are different. Try those. Figure out what you like / didn't like about the recipes and identify what was different. Then start to try and make some changes off the top of your head (this is particularly common if you don't have something in the recipe, leave it out? substitute?). 

Cook lots of different dishes. Branch out a little and try some different things. Stew, pastry, cake, stir fry, etc. Trying a bunch of different things will give you an idea of what happens when you cook something low and slow vs hot and fast, dry heat / wet heat, etc. 

What you are really looking for is a trusted source followed by experience, both in depth and in breadth. The trusted source is important to make sure you are getting experience doing the right thing. Ideally, maybe you should start with just depth and nail one dish / technique after another, but that's boring, and if you're doing it at home, you have to eat the results. So breadth helps the home cook, even if that isn't what you'd do in culinary school. 

Practice and learn and you'll get there eventually. Fortunately, you need to eat every day, so there's plenty of opportunity.