There are two main aspects to this strategy: Route planning and prospect management.

The least profitable part of the game is when you don't know your region's ports. When you first start the game you don't know where anything is. Get a hint at where a port is by accepting a prospect at the New Winchester bazaar. It will tell you what cardinal direction to follow to find a port. You can see each of you current prospects in the cargo hold screen. Remember that east means right on the map and west means left.

Use your scout sparingly: it eats your supplies. But if it does find something, investigate. You can find free cargo, which is good profit for you.

Once your chart has 3 or 4 ports, we can do proper route management. The goal is to visit as many ports as possible while spending as little fuel as possible before returning to New Winchester, all the while never visiting the same port twice.

You want to visit as many ports as possible because even if you have nothing to do there, you can write a port report, which is worth 100 sovereigns at the stations near New Winchester. This is also why we don't want to visit the same port twice: you can't write another port report until you turn in the one you already wrote.

What this means is you want to plan a route that looks a little like a circle. You try to visit a port you have business in, while visiting other ports on the way there. You then take a different route back so you can visit different ports, and write more port reports. Even if you do absolutely nothing except write port reports, you'll make more money than you spent on fuel and supplies.

The most important thing is to never, ever, make a beeline to the port you want to go to. Always visit ports on the way there and the way back. Make a slight deviation to loot that abandoned locomotive. Stop to fight that enemy you're sure you can take. Don't get tunnel vision.

The best way to make money is to buy low with bargains and sell high with prospects. Whenever you see a bargain, buy as much as you can afford. Bargains always cost less than what you can sell it for back at New Winchester, so it is always pure profit for you. You should keep a small emergency fund, but for the most part money in your pocket is money wasted.

After you take your goods back to New Winchester, don't sell them yet. Store it in the bank, and wait for a prospect that demands that resource. When a prospect you can fulfill comes around, try to incorporate it into your next planned route. If you need money now, you can sell it directly at New Winchester, and it will still sell for more than you bought it.

Other than this, the rest of money-making is really common sense. Don't take fights that cost more in repairs than net in loot. Mining/assaying equipment will improve your margins. Its better to fulfill prospects all at once. That sort of thing.

Now you know the basics of how to have a stable income. If you want to become truly rich or write the Song of the Sky you'll have to actually interact with the game's stories. But following this guide while you explore the horrors of the High Wilderness will keep you in the black.