Slane's Tips (Possible Spoilers)
Some of this information might seem obvious but sometimes even the smallest information can help, I'm not trying to teach anyone to such eggs, just sharing some minor wisdom.
If you wanna level easy then complete quest areas.
I personally take all the quests I can in all the areas I can, one I like to complete things and two if you take these quests you received more XP, Credits and level over the odds, by that I mean when you've completed a quest area you're usually higher then required for the next set of quests,which makes the next set of mobs/quests easier to complete, this doesn't effect the XP rewards if your still within the boundys of the map levels. (i.e. if you level 40 in a level 10 area you ain't going to get XP for the quests or very little).
Don't just run past mobs, I tend to attack creatures on the way to and from quests, this for two reasons, 1. I increases credits and level and 2. Killing creatures can open bonus quests for killing them.
Set your looting to area looting on a single click, you will loot everything and do it fast, this will save time and increase credits, if you follow the tips in the next section you should never have a full backpack, if you do for some reason get a full backpack take the time to either send your companion off or destroy the lowest value single loot, I don't get rid of stacks as you usually get lots of the same grey items in the same areas.
Remember to use all the fast travel driods and spawn points, this isn't WOW it won't bind you to one location.
At the moment you cannot chant advanced classes, you can respec within that class at an increasing credit cost, so think carefully what you want to do futher down the line. Within advanced classes you can have two skill sets, I.e. in the Adv. Bounty hunter tree you can DPS or HEAL, so at a cost of credits you can heal one flash point and DPS another, I warning though, it you continully do this the cost to respec will be large, i've heard personally of it getting above 37,000 credits, although I don't know if theres a cap or if there is what the cost is.
Open your 5000c backpack early....
The expanded space will allow you to hold more items before selling, which in turn will save you time, if you don't want to do this and you have your first companion while traversing the area (moving from one quest to another) send them off to sell your grey items, its usually quick and again will save you space.
I personally opened my 5000c and 20,000c backpack as soon as I had the money, and still had the credits to buy my speeder at level 25. I tend not to buy ANYTHING, as in I use loot from quest rewards and drops, I buy all my skills as i get them, but do not make the trip buck to the trainer as soon as I level, this is because I find that completing the current quests will take you back to the trainer location once completed and again saves you time to play or level fast if that's what you're after.
If you want to move across the map fast whether on a speeder of on foot then stay on the solid golden line, this route is clear of mobs, the dotted golden lines usually represent the routes to quest locations.
Save your Commendations....
Not a lot of people don't know that you can trade these up to the next level/map area at a cost of 2-1, example you have 10 Hutta commendations, you can change these for 5 Dromund Kaas commendations.
Don't forget that your 'slave' levels with you, so remember to upgrade their equipment too, its very easy to forget this, I know i have on occation.
Make use of thier time, If you've already got your crew skills then use then effectively, if you're running around the fleet looking for skills or selling items on the GTM then send them of missions, this is especially useful to do while you're in flashpoints.
If you increase you companions affection for you it will reduce crafting time and increase successfulness of gathering or completing missions.
Even if you tread them badly they will never leave you, your level also dictates how many companions you can have working on missions, I believe this is 2 at lvl 27. 3 at 37, 4 at 47 and 5 at 48-50. You don't have to have your crafting materials on you, they can be either in your bank, on the ship or on you for you to make things.
If you knew any of this that's cool, if you didn't hope it helps.
I will be updating this as I go along, but for now i have to goto work.