conscientious

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Guided by or in accordance with the dictates of conscience; principled.
• adjective Thorough and assiduous: synonym: diligent.

from The Century Dictionary.

• Conscious.
• Controlled by conscience; governed by a strict regard to the dictates of conscience, or by the known or supposed rules of right and wrong: as, a conscientious judgė.
• Regulated by conscience; according to the dictates of conscience; springing from conscience: as, a conscientious scruple.
• Synonyms and Scrupulous, exact, careful, faithful, upright, honest, honorable, righteous.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Influenced by conscience; governed by a strict regard to the dictates of conscience, or by the known or supposed rules of right and wrong; -- said of a person.
• adjective Characterized by a regard to conscience; conformed to the dictates of conscience; -- said of actions.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Thorough, careful, or vigilant; implies a desire to do a task well.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective guided by or in accordance with conscience or sense of right and wrong
• adjective characterized by extreme care and great effort