So you've been mining for a little while, gotten acquainted to the controls and made a bit of cash, but you want more. Lots and lots more.
Welcome to the Trading guide.
Let's do some capitalism.
Trading, in itself, is very easy - it boils down to "haul goods from point A to point B, buying low and selling high" after all - but maximising profits over time isn't as straightforward and will require you to know a few things.
We'll cover those later; for now, let's review the basics.
Buy low, sell high.
About as obvious as it gets, this one; make use of your Trade Routes tab to know where to drop off your goods.
ALWAYS keep in mind how far your destinations are.
Even if some selling point would net you the highest profits in Sirius, it doesn't matter if getting there would take a hour - by the time you've docked there, chances are you may have taken two or more shorter trips and sold your cargo for less, but also made a lot more cash in the process because it was much faster than the alternative.
Never, EVER, make a return trip for free if you can help it.
While technically you are not losing credits by not bringing anything back, you are losing time - and time is the most precious commodity in the world. Don't waste your time.
Fly big. The bigger, the better.
When it comes to trading, it's just as much about the size (of your cargo hold) as it is using it; therefore it is in your best interest to go for the biggest transports you can acquire for your faction ID.
Point four warrants a little more attention, so let's digress a little.
Picking your next transport isn't as easy as going to a station and buying the first thing with a bigger cargo hold than the one you currently have; buying ships costs a lot more than you get back by trading in your old one, so it's a good idea to look carefully at the list of available transports on the Discovery Freelancer wiki.
As you can see, there's a lot of choice here. While you could simply go with the prettiest one you can find, and that's an entirely valid course of action, here we want to maximise profits; in order to do that, we'll have to pick the ships giving the most bang for your buck.
How do we determine which ones would fit the bill? Simple enough: first of all, divide their asking price for the size of their cargo hold and compare the results of those you're interested in; a bigger number means you're paying more for every single point of cargo hold.
For instance, let's examine a few 'relevant' picks:
Gull, 1.000 cargo; the entry-level-est of trading vessels, generally skipped (4.600.090 / 1000 = 4600)
Bumblebee, 1.800 cargo; THE actual entry-level trading vessel (7.100.096 / 1800 = 3945)
Mammoth, 2.200 cargo; widely available and not much more expensive than the Bumblebee for a nifty +400 cargo (10.100.095 / 2200 = 4591)
Percheron, 2.500 cargo; the biggest one in the 'cheap light transport' bracket, bit more expensive than the Mammoth but also +300 cargo (12.600.095 / 2500 = 5040)
Hegemon, 2.750 cargo; a mining vessel, not particularly suited to trading because of its unwieldy size, but still has the cargo hold for it (18.100.090 / 2750 = 6582)
Serenity, 3.600 cargo; biggest legitimate transport available to Freelancers (39.100.096 / 3600 = 10861)
As you may have noticed, the results of the division tend to increase across the board.
That's normal and expected, and so long as the increase is relatively steady (e.g.: Bumblebee to Mammoth to Percheron) that's alright, whereas significant spikes (e.g.: Big Dragon) are a red flag.
My recommendation is to be patient and mine for that little bit of extra cash you need to get your first significant upgrade (e.g.: Sunburst to Percheron), even if there are cheaper but smaller ships you could already get. You can wait for a few million credits more.
Now, the next thing to consider would be who uses those ships and what is your ID.
Your ID is one of the most important things in the game, and it'll come up again later. It dictates what you are allowed to do and what you are not; this means that as a Freelancer, you can't use any of the largest transports (the Pirate Train and l'Ane, while bigger than a Serenity, still aren't the biggest) and that you do not have access to any factional shipping bonuses. Check them out HERE, it's important.
This won't do.
No, to maximise profits properly, we don't settle for anything but THE biggest - buying smaller and cheaper transports in the interim is fine and will speed up your cash flow, but the end goals are the 5kers you may have heard veterans mention (as in, 5000 cargo hold).
This means you'll have to sign up with a faction with access to said 5k transports, and have a lot of credits in the bank to afford them.
Which one should you pick, among the 5kers? Ideally, the one that best suits your trade route and your ID shipping bonuses; that aside, you'll notice how all of these have different loadouts and with a greater amount of guns, the cost likewise increases.
No, you're not a warship. No, you're not a combat transport either.
Yes, you're bomber food. Yes, the guns will help a little (protip: kill hostile NPCs if you find them around stations or gates, it's free real estate!), but if you want to be safe from pirates, you'll want an actual escort.
So you've finally purchased your 5k transport and you have the appropriate faction ID. By now you know basically everything there is to know about lawful trading and make loads 'a mahney.
But what if you didn't want to stick to those shipping bonuses and instead trade something different?
Shipping bonuses aren't the be-all and end-all. They're a hefty incentive for shipping factions, but maybe you want to ship something different.
Something that's not covered by the bonuses, for instance, to fulfil a player-made supplying request you saw on the forums; something illegal, perhaps, for a spot of smuggling; or perhaps simply something that's not covered by the bonuses but would fit your personal RP (and make cash in the process).
In this case you may want to consider transports that ARE NOT part of the 5k club.
Like liners, which are more heavily armed and armoured transports that are in-universe equipped to carry people.
Ferrying passengers around WITHOUT a liner is illegal in all houses and will net you substantial fines or worse, on top of being somewhat nonsensical from a RP perspective (imagine sticking living people in a container; even if you're the worst scum in the world you probably want your cargo to be alive when it gets dropped off, or you won't be in business for long).
Alternatively, if you like to cruise on the wild side, why not a combat transport? Sure their holds are smaller than a 5ker's, but they're also a signficant threat to would-be pirates (or even law enforcers!) due to the sheer amount of gun they can bring to bear. If you're expecting resistance or want to cargo pirate some poor sap, these are definitely worth considering.
The last thing to cover would be a somewhat contentious tool, named FLCompanion.
While it can pull up a lot of information from the entire game, it is mostly used for its very handy credit/second calculator, for obvious reasons: making every second count as much as possible. Why is it contentious? Because it's kind of spoiling the fun of figuring out these routes by yourself, in a game called Discovery Freelancer.
Nobody will stop you from using it, of course, but if you'd rather discover things by yourself - don't.
And that's about it for trading!
If there's one last thing to note, it's about what you should NOT do - be a silent trader.
The name, silent trader, more or less speaks for itself: it refers to the sort of player who just flies around and trades constantly without bothering to RP, or even just respond to hails and greetings from fellow players.
Nobody expects a lenghty and fulfilling conversation from a trader that's moving around systems (your possible convoy-mates might) of course, since typing makes navigation somewhat difficult at times, but people will appreciate the consideration when you reply to their greetings or, even better, stop and chat for a little while.
Brigthen a lawful's day by RPing with them. Those poor police fellows will welcome the diversion.
Brighten an unlawful's day by RPing with them too, even! Don't just try to run away or haggle - not all pirates only want your credits! You could even talk them out of pirating you, perhaps even strike a bargain. You don't know until you try!