I have some other suggestions:
Focus on activities for which you have a comparative advantage and outsource whatever else you can. Exploit your edges! Also, spend a significant amount of your time and resources increasing your comparative advantage(s). Become as much of an expert as possible at whatever you are focusing on, though this works better if whatever you are focusing on has increasing returns to expertise. So for instance, getting to the top .1% of programmers is worth a lot compared to even being in the top 1%, but being in the top .1% of elementary school teachers probably not so much.
That shouldn't discourage you from giving random stuff a try sometimes but I think that should get a limited amount of resources. What I have mostly learned from trying out a lot of different things is that most things are a lot harder than I think they will be. Trying to make money off a website and failing will teach you some things, but probably not the valuable secrets that people who actually make a lot of money off of websites know. In my opinion if you want to maximize your value to the world, or to yourself, you should aim to maximize the number of valuable secrets* you know and can exploit. In my experience you have to really specialize to learn those secrets so that should dominate your productive time.
Another suggestion, somewhat related, is that you should focus on the activities that have the highest expected monetary reward. Prices are a valuable signal that represent the collected wisdom of a lot of reasonably rational actors. They should be an important part of your calculation of how to spend your time. In other words, if someone is willing to hand you a pile of money to do something, that probably means they have thought long and hard about it and consider whatever they want you to do to be very valuable. You should think long and hard about it before you decide that some other activity that no one is willing to pay you anything for is actually more valuable.
*maybe rare knowledge is a better term, since they don't literally have to be secret, just unknown to most non-experts and difficult to discover.
...Another suggestion, somewhat related, is that you should focus on the activities that have the highest expected monetary reward. Prices are a valuable signal that represent the collected wisdom of a lot of reasonably rational actors. They should be an important part of your calculation of how to spend your time. In other words, if someone is willing to hand you a pile of money to do something, that probably means they have thought long and hard about it and consider whatever they want you to do to be very valuable. You should think long and hard about it
If you're like me, you have way more ideas for things to do than time, energy, and willpower to do them with. (And if you're not like me, you might very well become like me if you just kept track of all the times you or someone else said "Hey, that might be a worthwhile project.") To give you an idea of what I'm talking about, here are some entries on my things-to-possibly-do list: give speed reading another shot; improve the Less Wrong codebase and add a feature that helps users find old, good posts they haven't read; experiment with online freelancing work; try my hand at e-commerce; work as a salesperson to build social skills.
One of the things I've learned from keeping a things-to-possibly-do list is that doing stuff inevitably takes longer than I intuitively think it will. For example, the main thing I did during the past 3-day weekend was write 36 Anki cards and 220 lines of Python to program myself and my computer to help me keep a resolution. In past years, I might have gotten demoralized halfway through, thinking things were taking too long, but I've gradually gotten used to things taking longer than I expect.
Given that things take such a long time to get done, it seems worthwhile to spend a decent amount of time deciding what to work on. But the standard objective of doing whatever has the highest expected utility is often computationally intractable in practice. For example, what's the expected utility of building social skills?
Given this, I'm working on a list of heuristics for the computationally intractable problem of what to work on. Here's my current list; feel free to suggest additions in the comments.
Further Reading