Whenever I do squats I am so intent on making a straight back I feel like I am over-exaggerating my posture. The end result is, instead of a slouched back I feel like my back is arching to far in the other direction. Is this something I should be worried about or fix? If this is something that needs to be fixed, what is the best technique for making sure my back is straight and not curved (in either direction).
Don't overextend the back while squatting (or deadlifting, or any other heavy lifting*). I used to hyperextend my back by over-firing my spinal erectors, which caused overarching in my lumbar spine. I of course could not maintain this position at the bottom of the squat, causing me to go from hyperextended to flat while under load, which is Not A Good Idea and caused pain and soreness. Don't do that.
Kelly Starrett's One Joint Rule applies here. I recommend studying the concept deeply. My pre-squat cues, gleaned from Starrett's Mobility Workout of the Day video, consist of the following:
This gave me a flat back instead of a hyperextended one. The back should stay locked in this neutral position for the entirety of the squat. Another one of his other MWOD videos goes into extreme detail on this process and I highly recommend it.