How can I earn lots of credits?

This answer is out of date.

With the recent nerf to Slicing, it is, at best, breakeven to run lockbox missions. Slicing can still be a money maker thanks to slicing nodes in the open world, and, accounting for crits, if you only run bountiful lockbox missions so I'm keeping this answer up, but it's hardly the best way to earn money anymore.

So far, the best results I've had have come from Slicing. Before I get into what makes Slicing so effective, I want to point out why I've had limited success with other tradeskills:

Other Gathering and Mission Skills have two key issues. Firstly, here's an upfront investment, in credits, required to do any sort of substantial gathering. This puts a floor on the price for which you can sell your goods at a profit, and that floor is actually fairly high. Furthermore, the Galactic Trade Network is atrocious. The UI is horrible for searching for specific items or for selling or purchasing decent sized quantities. What this means is that for you, the seller, your pool of available buyers has shrunk. Worse yet, because the game is so new and the economy is not yet mature, there are a ton of people simply dumping these materials on the GTN at 'below cost' - they're just trying to recoup some of their investment as they power through to the next skill tier, or dump the mats they didn't end up using while leveling Synthweaving or Armsmech or whatever.

Crafting skills are in a similar bind - while these are likely going to be the most profitable in the long run - especially with the ability to sell 'crit' crafted items with an extra augment slot - as of now, crafting requires a fairly massive upfront sink in both time and credits. Furthermore, most crafted goods are easily replacable by items from token vendors. Simply do a few warzones or flashpoints or some quests, and you'll be swimming in mods and orange gear to slot them in. Additionally, an immature economy means there isn't much demand for high level items just yet, and the market for low level stuff is flooded. Add to this the aforementioned problems with the GTN, and crafting, while it has a high potential upside, again lags behind.

Which brings us to Slicing. First off, I want to be clear here: Slicing isn't spectacular money, and it's not particularly fast money, but what it is is easy money. That is to say: Slicing is great because it doesn't require any interaction with the larger economy, is reliably profitable, and delivers it's rewards directly in the form of credits.

So, How do you make money with Slicing?

It's pretty simple really. The key is to, first off, always be running missions (obviously), and specifically, always be running missions that reward Lockboxes - especially those labelled as Rich and Bountiful. Interestingly, higher level missions are not always more profitable. For example, the bountiful missions listed as levels 41-48, His Home is his Castle and Off The Grid, will yield a smaller profit than the level 33-40 bountiful missions, Be Careful What You Read and Pointing Fingers. While they are still profitable (and thus, worth doing for the skill increase if that's of value to you), they will make you substantially less money than alternatives.

This Spreadsheet, compiled by the excellent folks in <Revenge of the Jerks> does an excellent job of laying out exactly which missions are the most profitable, both in terms of raw credits, and in terms of credits/minute.

TL;DR: Slicing provides the simplest and easiest way to make tons of credits with a minimum of fuss. While other professions will eventually be more profitable as the game matures, at this time, Slicing clearly provides the most reliable monetary benefit - and should continue to be a no-fuss, no-muss, reliably profitable option for solo players as time goes on.

I just ran my level 22 daily space missions (all 5 of them), with the daily quest rewards. It took 30 minutes.

• Credits - 7265 earned
• Xp - 33259 earned (15000 rested xp was not touched)

On top of this, I earned ~20 fleet commendations. With those, I can buy a level 50 green random bag worth 1400 straight to the vendor, or 1300-1500 if I open it and vendor the item.

This activity yields ~17000 credits/hour with the daily space missions at level 22.

One of the missions awards 600 credits for completion and can be run in 6 minutes. Another one awards 300 credits for 3 minutes. Repeatedly running either one gives 6000 credits per hour without the daily space missions at level 22.

The most efficient and quickest way to earn credits in the end-game comes from dailies and the new(4.0) Heroic quests system, and for the more active player; Operations.

• Dailies are short quests that can be repeated on a daily basis and give you 6-10k depending in the planet and if you do the bonus quest or not. Dailies can be done on the planets: Corellia (black hole), Belsavis(section X), Cz-198, Rishi, Yavin 4, Makeb and Oricon. Each of these planets has a fast travel terminal that will take you to another dailie questing area/planet. Link to all dailies
• The new heroic system allows you to do heroic +2 quests once a week, nearly all of these can be done solo with a decent companion and will give you 18k per quest and another 12k if you do the bonus (not all
  quests have a bonus quest). Some quest are quick and easy, i recommend doing these first. While others take a while to do or require a long walk/kill ratio to complete.
• If you are in a guild and do Operations frequently without wiping to much, you can also build up quite a few credits on a single run, this is probably less efficient than the previous 2 options if you compare the time/credit ratio. The same is for doing Flashpoints, they give credits, but take a while to complete.
• PvP games is also an option but being decent at PvP will require a separate set of gear with expertise on it. Winning a game will give you 15k credits and the average PvP game lasts 15 minutes. Losing a game will only give you 7k credits. Time/Credit ratio is, again, lower than the first 2 options.

Other ways to earn credits are:

• Playing the GTN (differences from server to server and time to time, Also takes some 'skill' to to do this) this is a slower option to gain credits.
• Grinding crafting materials, through open world gathering or crew missions, and selling these on the GTN (prices again variate from server to server)
• Grinding mobs, not as efficient anymore because BW decreased loot from mobs to counter gold sellers/farmers/bots.
• Just playing the game; by simply doing a lot of quests while you level, you should be able to get a nice amount of credits by the time you hit your level cap and this should be enough to get you everything you need while you level. A lot of the credit sinks that tormented lower levels has been removed such as not having to pay anymore for new skills and abilities and leveling has been made a lot easier and faster, meaning the content is generally a lot easier than it was at the time that the original question was asked.

Slicing and Treasure Hunting are great for money, I recommend both.

I've had some good results selling guns on the GTN, but nothing so far has compared to just running the missions. Every new planet (and level) seems to result in so much more money that hanging out examining prices doesn't pay off.

If you dig the money game, that's different. But the quests seem to hand out good enough cash to pay for speeders & skills, provided I don't get too spendy on crew skill missions.

You can do the following things as said in this guide to making millions of credits:

• Resell on the Galactic Trade Network.

• Always have your companions out doing crew skills when you don’t need them.

• Create more alts. Choose different crew skills on them all. This will allow you to get a bigger % of the market to earn from.

• Do Space Missions from your ship daily.

• Do Daily quests. This is one of the fastest ways of earning credits.

• Loot everything. Sell all trash to vendors. Save greens or better for the GTN, if they don’t sell after a few listings just vendor them.

• Do PvP warzones. These can provide you with some good coin.

• While leveling 1 -40 don’t buy much gear. Get the gear you need from quests, drops and PvP. This saves you a lot of money.

• [Slicing] Slicing is a great way to make money. Go to a level appropriate zone and start working.

• At level 50. Go to a lower level planet like Quesh and kill everything on the planet and loot.

At this fancy site (maybe the official website for swtor?), it says to do (Full explanations at site):

• Galactic Trade Network (GTN)

• Gathering & Mission Skills

• Services

• Questing

• Dailies

I've found that the gtn is the best way to make money. i agree that missions, warzones, and flashpoints give a good amount of money (especially with the dailies) but selling any unwanted, unbound items at the gtn gives you lots of money. just pay attention to how much the other players selling the same item are selling it for and even if you down your price a bit it will still make you plenty back.

if you craft and do crew missions like treasure hunting, archeology, etc. and sell anything you don't use you will make lots of that money back. selling things you craft will make you tons of cash as well (especially when you start crafting prototype and artifact items).

just note you will need a bit of starting cash to sell items on the gtn though, but as an example, i had about 5-6k credits to start, after putting a couple artifact items on the gtn, i came away (after they were sold of course) with 50k+ credits.

certain items (like tatooine flamegems) sell in small groups better too so watch that as well. selling the same thing over and over can help as well so you can see how much you can put up as a price and still sell. and always keep in mind supply and demand (especially demand).

do note also that however long you put an item up, if it doesn't sell the first time just keep putting it up, it will sell evetually. you get your deposit back every time the item expires so you can put it up as many times as you want. also, if it doesn't sell and expires you can adjust the price when it expires. just don't cancel a sale once it's up or you'll lose your deposit.

again with this i've made quite a bit of extra money and it has worked very well for me so far. little work but big payoff.