You have three types of abilities... 'normal' attacks, 'special' attacks and for your Sentinel, 'force' attacks.
Normal and special attacks are the white numbers, and force/tech attacks are yellow.
Your yellow attacks will never miss, but can be dodged/parried. Yellow attacks have a base 100% accuracy and any +accuracy you add will lessen the chance for those abilities to be dodged/parried.
Your normal/special 'white' attacks are different. 'Normal' attacks, which for the most part, only include your auto attack (slash, rapid shots, etc.) while your special attacks are pretty much everything else. 'Normal' attacks have a base 90% accuracy while 'special' attacks have a base 100%. 'Special' attacks work the same as 'force/tech' attacks in that they will never miss, but can be dodged/parried.
If you hover over your accuracy stat in both melee/ranged attacks, you'll see the number difference between 'normal' and 'special.'
To answer your question, you want 100% MELEE/RANGED ACCURACY. Don't concern yourself with force/tech accuracy. To clarify, when you open your character window and look under melee/ranged without hovering or clicking on anything, you want that number to 100%.
For example on my Mercenary, I have 100.27% ranged accuracy with an accuracy rating of 300.0.