Use the Force is an incredibly awesome skill. With the right talents, you can use it to replace: Perception, Initiative, Deception, Persuade, Pilot and possibly more (that's just off the top of my head). As well, it's the trigger for using most of your force powers. A decent to good charisma and skill focus are highly recommended.
This.
If you have ridiculous enough stats you can quite possibly use all three rape options.
With a 56 point buy I'd do this:
Str: 16
Dex: 14
Con: 15
Int: 14
Wis: 16
Cha: 18
Each time you get your two level-based stat bumps, one goes into Charisma, until it hits 22. The other one can first shore up Con, then the rest can go into Wisdom if you find you prefer force powers or Strength if you find you prefer lightsaber combat.
Be a human Jedi, start with at least one Force Training, and probably Skill Focus (Use the Force). That feat is more or less mandatory if you plan to do anything with force powers, especially if you are starting at low levels. With a decent enough Charisma nobody's defenses will be high enough to resist you. It's almost campaign-breaking, so be careful.
If it looks like core will be your only option, pick up Weapon Focus and Specialization (lightsabers), in preparation for going into Jedi Knight for the Juyo talent. Once per encounter, you can spend one Force point, pick a target, and roll twice the first attack you make against him every round for the rest of the encounter AND keep the better result. It's probably the best lightsaber talent in any book. Also consider the Soresu talent, which basically the same thing for every time you Block or Deflect (Block and Deflect are also probably mandatory if you are using a lightsaber, since your own defenses will likely be crap).
If it looks like Threats of the Galaxy will be available you can skip Jedi Knight and get the same thing from Sith Apprentice using the Stolen Form talent from that book. Otherwise, Jedi Knights don't lose anything for later gaining dark side points, and nothing says that you can't study the Jedi ways and also be a Sith (and/or a former Jedi). Like others have said, you will probably want Dark Healing from Sith Apprentice anyway. Dark Side Adpet, which lets you reroll Use the Force checks for dark side powers may be worth it as well, even if Force Lightning is your only dark side power.
See about expanding your books as soon as possible. The real showstopping abilities, like Force Thrusting an AT-ST into the stormtrooper regimen behind it and using Move Object to tear low-flying starfighters out of the sky, come from the Force Unleashed book (those powers require you to use the Destiny character option, so plan for it if that appeals to you).
Also note that if your character has basically no morals, a cleverly worded Mind Trick can replace most social interaction as well, depending on how the DM interprets the entry.
Specifically this:
-"You make an otherwise unpalatable suggestion seem completely reasonable to the target." and "The target won't realize later that what it did was unacceptable."
Seriously. The only way to balance this is to explain to your DM that "Infiltrating the enemy base" should be one big long encounter so you aren't tempted to just tell every guard you see that you are part of a surprise inspection team and belong here ("Of course you don't need to see my identification..." /handwave).
EDIT: Also note that if you DM is not adjusting things to allow you to play bad guys, Sith Apprentice and all related classes have insanely stringent requirements. the general rules state that if your Dark side score ever exceeds your Wisdom score the DM is supposed to take over your character and have you reroll. Sith Apprentice requires your Dark side score to equal your wisdom score just to qualify for it, and takes away all your abilities/feats/powers that you gained from levels in that class if that ever changes.
Essentially what this means is that by RAW, the moment you use Force Lightning as a Sith Apprentice you must atone for it by spending a Force point immediately or lose your character. In addition, upon leveling up and putting a stat point into Wisdom, you must then immediately kill a kitten.
