Hey there,
Feedback is a
direct result of amp's (or PA)
volume and the guitar's
proximity (and location) with regard to the amp (or floor monitor, or PA speaker). With regard to feedback through a system, an electric is fundamentally different --a
world apart-- from an acoustic with the former requiring much "more" to induce feedback; the latter needing very "little" to result in feedback.
1. Put your amp across the room from where you are playing, and start with a
low volume.
2. Raise volume to where you want and see what you get.
3. Volume and proximity is the big deal. After these points are addressed, you can focus on isolating the offending frequency that is feeding back. You said "screeching" which sounds to me like you are describing high-pitched feedback; this, as opposed to low-end feedback which is very common for acoustics. But identifying the frequency is tertiary:
always address the aforementioned main factors first.
Chime back in and let us know what happens ...you know, some feedback

Edward