With the multiple Slicing nerfs since beta, earning credits via missions is now not really viable without a maxed skill, full crew of companions and a lot
of micromanagement. Basically the only really profitable missions in pure terms of ROI are the level 1 & 2 moderate missions, as well as the level 5 moderate/rich missions. Have a look at these -
For Slicing now you want to focus almost exclusively on harvesting to both level the skill and make money. This is quite doable, you just have to know when and where to do it. The things to keep in mind are as follows:
- While other resource nodes are on about a 4 minute respawn timer, Slicing nodes are now on a 10-15 min respawn timer. Whereas with other harvesting skills you can often do multiple sweeps of an area, with Slicing don't bother - just keep moving.
- Expect that pretty much every other player you see will have Slicing and thus will be directly competing with you for resources. Expect that every other player is a complete and utter bastard who will ninja your Slicing node while you are soloing the pack of Elites guarding it. This happens with pretty much everything anyway (like quest objectives and chests), but when it comes to Slicing nodes any shred of courtesy towards other players apparently goes out the window. To mitigate this, it pays to play at non-peak times (in the US). I have a natural advantage being on the opposite side of the world as my main play time is late night/early morning in the US west coast. Fewer players means more nodes for you. Also, as a secondary benefit, less ninja-ing of quest objectives. If you are going back to a place specifically to do a "Slicing run", that is the time to do it.
- Keep an eye on your mini-map. Less a problem early on, but once you have a speeder you will often be moving long distances back and forth between areas and invariably not paying much attention. Scroll your mini-map out as far as it will go (mouseover and use scroll wheel) and watch for the asterisk-like harvesting node icons.
- Know the spawn areas. While in some areas you get Slicing nodes out in the middle of nowhere, generally the spawns are more frequent around "civilised" areas like buildings and such. The direct result of this is that, unlike other resource nodes, some planets have an extremely high density of Slicing nodes clustered around some points. Alderaan in particular seems to be a hot spot for this sort of spawn pattern. If you find a place like this, file it away to come back to at 3am or after a server reboot.
- Expect resistance. Slicing nodes will generally be far more likely to be guarded by mobs than other resource nodes. In particular, pretty much any place you see an Elite there will invariably be a Slicing node right next to him. Heroic areas are thus often quite good sources of Slicing nodes. To efficiently harvest in these areas, you'll likely need to be by yourself and a few levels over whatever mobs are around. Groups generally make harvesting impractical, often intent on blazing ahead like a bull in china shop without even stopping to heal, much less harvest nodes *cough*Lynk*cough*.
For missions, focus on augments. You'll likely find that the majority of these will be useless for your class, but you should be able to sell them on the GTN (especially the purples). Keep any that have stats of use for when you get a augment slotted item (I can craft you earpieces with augment slots). The other thing you'll get with critical successes (both with missions and nodes) is crew skill mission discoveries. These generally sell pretty quickly on the GTN, in my experience especially Bioanalysis and Treasure Hunting (I assume Underworld Trading and Investigation too, but I keep those for my alts). I have found that Diplomacy ones don't seem to sell as well. You'll occasionally get missions for the gathering skills too, like Scavenging and Slicing itself. Again, I generally keep these for myself or alts. You'll also get ship part and custom speeder schematics on crits. Unfortunately there seem to only be like a dozen or so of these in total, so subsequently the GTN is flooded with them. If you want these to sell you'll have to mark down the price to undercut everyone else.
For Treasure Hunting, absolutely avoid the lockboxes. I don't have any hard data, but I think the general consensus is these are even worse than the Slicing ones. Unless you are trying to harvest blue/purple gems for Artifice alts or selling on the GTN, focus on companion gifts. You can either use these yourself (make sure to use a guide for which type is best for which companion) or sell them on the GTN. Most sell pretty well as long as you stick with the price the GTN auto-selects. What you really want though are the gift fragments. You get these when you crit. Multiples of these (12 green/premium, 6 blue/prototype, 8 purple/artifact) can be assembled into high quality gifts, and should sell for a bunch on the GTN.
EDIT: I just threw some augments I had in the bank on the GTN and ran a few missions of varying levels to test the numbers and it seems I will have to revise my earlier statement. Based on likely yields, selling price and mission costs, it doesn't seem like augments are actually very much use at all purely from a financial gain perspective. Stick to doing those missions solely for the purpose of your own usage. That takes me back to my original statement, which is that in its current guise, Slicing is really only worth focusing on harvesting nodes rather than missions.