How should I choose my next step as a cook?

In my view this is pretty simple: make things you want to eat.

As long as you cast your net wide enough as you look for recipe ideas, there will always be new things that you'd love to eat and will learn something from making. And as long as you want to eat the food, you'll be motivated enough to actually follow through and do it.

Most of the time, this will mean making things where you're mostly comfortable with the recipe, but there are some new parts you haven't tried before. It might be new combinations of ingredients and flavors, which will broaden the creative side of your cooking. It might be new techniques, which will enable you to make more things in the future. To oversimplify, when you look at a recipe, if practically every step sounds new or difficult, maybe save it for later; if most of it gives you an "I can do this" feeling, go for it!

It's fine to take on bigger projects too, of course, as long as you go into it with the understanding that you might want to try parts of it by themselves first (or that things might fail the first time).

Either way, be sure to cast a wide net: skim cookbooks, read food blogs, browse recipe database sites or food photography sites, and so on. There's always a lot out there that you'll surely want to try and just don't know it yet.

But above all, just seek out things that look good to you (or your friends/family). The rest will follow.

This is really going to depend on where you're headed. What direction do you want your next step to be in? I think generally knowledge like this will flow pretty organically:

1. You know how to roast a chicken.
2. Decide you want your chicken to be more moist.
3. Learn how to braise a chicken.
4. Decide you want to add more flavor to your braise.
5. Learn how to make stock.
6. Decide you want to make better stock.
7. Learn how to break down chicken for bones, research different seasonings for stock.

Etc. Generally, find something you want to make, make sure you know how to perform most of the instructions, give it a shot. The most important factor in determining your next step is your interest in learning it. If you really want to make genoise but have no cake experience, you might make a couple of messed up cakes on the way, but you'll get there.

This is a difficult question to answer.

I you can roast a chicken, try stewing... if you can fry, try poaching instead.

You want to "step up your game" by learning new techniques or by learning new recipes?

IMO, the penultimate are desserts and in particular pastries and confectioneries where techniques and measurements are really important.

I would learn to poach fishes. I would learn to make pasta, and in particular stuffed pasta. I would learn to make a proper sauce (french sauce bases) I would learn to do a Italian ragu. I would learn to make a beef consommé from scratch.

Try recipes with ingredients and spices you are not familiar with (asian, middle-east...)

If you can I can roast a chicken, bake bread, improvise a dinner with what's in the fridge, etc...you've got some skills. So, the question becomes...what is your goal? You clearly can follow recipes, but want to get better. I would take several approaches to upping your game. First, search for techniques that you are less comfortable with. Find recipes that use these techniques if you like. Broaden your skill base. Second, venture into the cooking of dishes from cultures you are less familiar with. This will force you to use new techniques, but also new ingredients, which will improve your palate. Third, investigate flavors and think about ingredient combinations. This will allow you to create without recipes. Google "The Flavor Bible", for example. Finally, eat out as frequently as possible, vary the type of cuisine, pay attention to what you see on the plate and experience as a diner.

Don't worry if something appears too ambitious...you will learn more from failing...and you will likely to be able to eat the mistakes anyway.

If you really want to do this, you have to become a pedagogue first and train yourself in cooking second. This involves:

• Decide which specific skill you want to work on. Example: judge the doneness of pie crusts.
• Read the theory on the subject. Yes, there are books which explain how pie crusts work.
• Assess how far you are in your current skill. How frequently are your pie crusts done well?
• Seek for recipes which will require you to use that skill. Since you've read the theory, you are aware which set of recipes will need to cover in order to gain the skill. For pie crusts, you'll probably want to exercise simple flaky, simple shortbread, "wet" shortbreads (with egg, alcohol, and other liquids), crusts started from frozen, and crusts containing ingredients which change the browning behavior (soda, vinegar, sugar).
• Make these recipes until you are getting consistently good results.
• Document your cooking, noting what went wrong, and exercising that part more.

Of course, you will have a bit of trouble, because self-teaching does require some bootstrapping. As a novice, it is especially hard to properly decide what is a single skill and what is a combination of many skills, and also which situations are important to train for a skill. But it can be done, and done successfully.

This is known as "deliberate practice" and is the normal way to become an expert in a field, so that in 20 years, you will have 20 years of experience and not one year of experience, repeated 20 times.

If you are thinking "this is a lot of effort, I don't want to do it", I agree. Most people don't need to become cooking experts, and following the above regimen is quite superfluous for them. They do as Jefromi suggested, cooking whatever they like, and soaking up whatever nugget of cooking knowledge they notice along the way. So slowly, they become better cooks.

So why I am writing all this? Because this is what you asked for. Specifically, this is the way to avoid making recipes which are neither so easy that you teach you nothing, nor so hard that you fail to realize what they are teaching you, or even simply mess them up. You can either consciously organize an effective learning process for yourself and have an effective learning process, or simply cook with the side effect of learning now and then. It's your decision which you choose, the restriction is simply that, unless you pay a personal cooking coach, you can't have it both at once.

My suggestion and how my husband and I got started with cooking was Cooks Illustrated (and their various other outlets like Americas Test Kitchen).

By spending a year reading their articles and cooking their recipes, we learned a lot. We especially learned what to do and what not to do. Having those knowledge building blocks, we could take random recipes from the internet and make them with confidence knowing we only needed the ingredients list as well as feeling comfortable in taking on new food combinations we have never tried to make.

Finding recipes and following their directions isn't always the best way to cook something IMHO.

If the recipes on the internet get too tame you can step up to Modernist Cuisine at Home and Sous Vide cooking methods.

I agree that making one's own stocks are critical in stepping up the taste of your cooking. Learning how to pressure cook stocks is very time saving say 45 minutes instead of 3 or more hours. Cooking sous vide (water oven) has opened up a whole new world for me and delivers a moister chicken than is otherwise possible.