This advice is based on the mistakes I made in a Beta weekend, and the most frequent “WTF?!” questions in general/guild chat.
1. Advanced Class
At level 10 your character will get an option of choosing one of two classes (e.g. the Sith Inquisitor can choose between the Sorcerer or the Assassin). This is a permanent, non-reversible choice. While you can reset your class talents in the game, the ability to change Advanced Class is not in the game, and might never be an option in the game. If you get this choice wrong, you will have to replay the character from level 1.
Related to this, make sure to train your advanced class skills when you level up. Advanced class skills are not displayed on the same page as your standard class skills, you need to hit a tab to bring up the advanced class skills. Don’t be the guy in a mid-teens heroic group/flashpoint, who has to spend twenty minutes running back to the trainer. Speaking of which, its probably worth checking the first time you do a flashpoint that everyone in the group has trained their advanced class skills.
2. Modifiable Gear.
You want to keep modifiable gear. Its called “Custom Gear” and its identifying colour in game is orange (yes, that’s the same colour as almost-impossible-to-get legendary gear in WoW). By adding modules into modifiable gear, low level items can remain competitive as you level. So if you like the look of something, you can keep it, rather than having to vendor it two levels later to equip something with better stats. You should get a class weapon that is modifiable on the way to Level 10 (for Jedi/Sith its a lightsabre).
To get modules, you will need an appropriate crafting skill, be friends with a crafter, or be willing to spend credits on modules for sale in the Galactic Market Kiosk (the Auction house). You may see people refer to the Galactic Market as “GM”, which in other games would be a “Game Master”, well, not here.
3. Bind Point Reset.
When you move to a new world, your bind point (what would be a hearth stone in WoW), resets to the bind point at the new world’s starport. So if you move from Coruscant to Taris, and hit your quick travel ability to jump to the bind point, you will end up on Trais, not Coruscant, even if Coruscant was the last place you deliberately set your bind point to. Quick travel has a 30 minute cooldown, so wasting it is annoying. Edit: bind points appear a bit more useful, when you use quick travel you get to choose which bidn point you want to go to on that world.
4. Time is Money.
One of the most effective things you can do to boost enjoyment of an MMORPG, is to ensure your character minimises travel time between locations on the game map.
Your starship is free, all you have to do is compete your class quests, and you should get it around level 15-16. Upgrades will cost you a bit though (see below). At Level 14 you will also get a 35 percent sprint/run ability while you are not engaged in combat, so its worth handing some quests in and going back to the class trainer when that happens.
At level 25, you can spend credits to purchase a speeder from a vendor (on most worlds or at your faction’s Fleet Headquarters). Rank 1 training grants a 90 percent speed boost and costs 40,000 credits, so you will want to have that much cash on hand when you reach Level 25. The speeder itself costs 8,000 credits (and if you purchased the Collector’s Edition you may want to save for the VIP speeder that costs 1.5 million credits). At Levels 40 and 50, you can purchase Rank 2 and 3 training for 100 and 110 percent speed increases (and you’ll want to have a pile of credits for this too).
Somewhat related, its worth spending a few credits on increasing your inventory space. The more you can carry the less often you have to stop questing and run to the vendors (and if you have your crew busy crafting and missioning while you are questing, your bags can fill with stuff quickly).
5. Ships, Ship Upgrades and Ship Quests.
My main advice here, is don’t try a ship combat mission without spending a few thousand credits on basic ship upgrades. Having more health, shields and weapons makes the missions significantly easier. Every quest I tried without upgrades installed was a complete failure.
While ships act as player housing, customisation is limited, the interior is unchangeable, but you can buy upgrades to improve your odds in combat. These are purchased from vendors at your Fleet Headquarters, but you actually need to take the upgrades back to your ship and then click on them to install them in your ship.
Ship quests can be picked up on board your ship. Ship quests are rail quests, and have been likened to an old computer game called “Starfox” (not one I played, but maybe you get the reference). Your ship follows exactly the same path through the mission zone, you have a limited ability to move up/down or left/right to avoid debris/asteroids/attacks, but mainly its about effectively targeting all the enemy ships and turning them into pixelated explosions. Hold the mouse button down to get continuous fire, unless you enjoy clicking mouse buttons three times a second.
Battles are short (under five minutes), not really PVP, earn you credits/XP and can fill time while you wait for other people to do stuff.
6. Crewskills
First, take a look at the guide here: http://www.skeletonjack.com/guides/crew-skills-for-swtor-made-simple/. Its the best one I have seen so far for gathering/crafting/mission skills in SWTOR (also called crewskills, as you get your crew/companions to do the work, as the designers said “Darth Vader doesn’t farm”).
“If money is all that you love, then that’s what you’ll receive.”
If you want to make easy credits, take Slicing. I have seen several people say that its the fastest way to make easy credits while levelling. Edit: the credits from slicing appear to have been balanced in line with other professions. Otherwise you can choose to be able to make yourself weapons or armour, but not both (at least on the same character, profession self-sufficiency is a major reason to level alts to support a main character). For the other skills my advice is:
Mission skills – don’t take these if you can’t stand unpredictable outcomes.
Armormech/Armstech – don’t take these if you are a force using class.
Artifice/Synthweaving – don’t take these if you are a non-force using class.
My expectations of the early game economy is that it will resemble a frontier/mining camp economy. Prices for everything will be ludicrously high in the first few weeks as people level their craft skills as rapidly as possible, while flicking the junk they have made onto unsuspecting marks for rip-off prices. I would recommend not buying anything off the GMK until you have you first speeder.
7. Companions
You should have one companion by Level 10 and a protocol droid companion on your ship when you get that around level 15-16. In my experience, companions work well out of the box, but its worth taking the time to learn a bit about your companion and what it can do. This pays off in social conversations, as you will have a better idea of what will gain/lose you favour with your companion.
Remember to upgrade the armor and weapons your companion has equipped (your protocol droid probably does not have a weapon when you first get it).
8. Quest rewards
You will often get a choice between an item of equipment, a lock box, commendations or equipment for companions. I don’t think there is a right or wrong answer here. Going for commendations will usually allow you to get one or more blue quality items by the time you finish a zone. Commendations can also be exchanged in at vendors, on a 2:1 basis, for a higher tier of commendations, so they are not completely wasted if you forget to spend them. But a solid green item upgrade now, can be worth more than a blue upgrade later.
A lockbox will get you a random item, could be good, could be crap.
Companion items can be useful, in that they will change the appearance of your companion, so that it does not look quite so much like the thousand other identical looking companions wandering the galaxy. In beta, I found it hard to find upgrades for companions, so be careful about passing over companion items.
9. Courtesy.
Treat others as you would like to be treated. Unlike WoW, SWTOR does not have an anonymous tool for quickly forming random groups for instanced content. If you spend a lot of time and effort alienating the other players on your server by acting like a dick, you will end up sitting alone in your spaceship. Remember that the behaviour you choose to display in game can get your account suspended or terminated.
My two specific tips here:
(1) in groups, do not roll need on an item unless it is an item you can use, and which is optimised for use by your class (if you pay attention to your quest rewards, you should figure out quickly what stats are optimal for each class).
(2) if you say you want to do a flashpoint/heroic group with someone, go and do it with them, do not make them wait for 30 minutes while you “finish just a few more quests”, “hand in just one more quest”, “Ooops, forgot to go to the trainer”, or “Hey, I forgot I have to make dinner, BRB”.
10. Patience.
Enjoy the journey in SWTOR, but have a Plan B for when the servers fall over/go offline for maintenance, or you have to wait for other people. I’ll be downloading a few extra books onto my Kindle to cope with any SWTOR withdrawal symptoms.
Mechanics Are Easy 
These are some solid SWTOR tips– thanks for sharing them!