The surviving Koine Greek corpus contains quite a lot of transcribed Semitic words, borrowed from Hebrew, Aramaic, and maybe others. (For example, the LXX is full of Hebrew names.)
Were there standard conventions for these transcriptions, either documented at the time, or derived from later analysis? For example, is there a consistent mapping between the three Hebrew dental stops (daleth, t'eth, and taw) and the three Greek dental stops (delta, theta, and tau)? Or is the transcription more ad-hoc, with e.g. some transcribers using theta and some using tau for the same Hebrew phoneme?