Five main factors in good Bible Translation are:
1. Objective. Integrity requires the translator preserve what the original language says, even when it apparently contradicts his own theological understanding, or that of groups with which he associates or which are funding him.
2. Ancient Manuscripts. A translation can be no better than the Hebrew or Greek manuscripts/text from which it is being made. (No critical edition of the Greek New Testament is yet perfect. The Nestle-Aland 27th or 28th edition would be a good place to start, though 1Corinthians 15:51 and Revelation 20:5 may likely need correction.) For Example: John 1:18 using Nestle-Aland is best and very precisely translated by NASB as, “God no one has seen ever! An only begotten god, the one being in the bosom of the Father, that one has explained him." This shocks most Bible translators, but the NASB translation is accurate.
3. Consistent/Concordant. Words should be translated as consistently as feasible, especially where it may have theological implications. A good example of inconsistency is the translations of Hades and Gehenna. Both should not be translated with the one English word, ‘hell.’ Hades, the state of the dead (until the resurrection), is in contrast with Gehenna (Matthew 18:9; translated in Revelation as ‘lake of fire’), those dead who will cease to exist. Hades can't equal Gehenna because Hades is "cast into the lake of fire (Gehenna) in Revelation 20:14.
4. Specific or Ambiguous? Languages often do not match word-for-word. Consider the Greek word, diathēkē. It means either ‘covenant’ or (last will and) ‘testament’ (Hebrews 9:15 versus 9:16-17). When used in the latter sense, it is proper to add a marginal note: ‘Or, covenant’.
5. Customs, Idioms, or Hebraisms. “Let not your heart be troubled” (John 14:1, 27) in some languages must idiomatically become “Let not your 'kidneys be troubled'” or even “Let not your 'spleen be troubled,'” though a marginal note should be added: ‘ * Literally, heart’. Other examples would include: Giving of a shoe to make a covenant (Ruth 4:7-8). This becomes understandable when a translator knows the ancient custom. Also, Melchizedek would seem to be non-human (Hebrews 7:1-3) without understanding Hebrew expression that his biography is not recorded.
The most successful efforts at accurate English translations include: RVIC (Revised Version Improved and Corrected, https://herald-magazine.com/christian-literature/online-bible/), Rotherham; and New Testament Diaglotts (interlinear only): McReynolds, Marshall, Concordant, and Kingdom Interlinear.