Like Vek said, its all about form and starting low with small increases. I've been following the Starting Strength program for over a year and see improvements. I started low and ensured form before adding weight. Other than knotting up my shoulder last spring because the bar was too low on my back, I've not had any issues. When I changed over to more cardio as the weather broke, I felt stronger and my distances increased better than in past years. I also think the program helped a lot trekking the mountains of MT last fall. Just my experience...
That said, I watched a guy and his girlfriend try to wreck their backs while I was waiting for the squat rack. He did good form squats with warm up but really struggled with higher weights even at 1/2 squat depth. Loose belt, no valsalva, it was bad to watch. They started turning into good mornings quick. Deads were a variation of sumo and squats with a rounded back. Wanted to say something but learned that lesson last year.
Yep. Form is critical. Also, proper form isn't the same, or at least, it doesn't necessarily look the same for everyone. Body proportions affect proper form for the individual. Often people try to show someone how to do squats without taking body proportions into account. So they try to emulate the model's good form which works for his body, but impossible for their own, and end up doing them dangerously for themselves. Here's a good source of info on it: How femur length affects squat mechanics.
Couple of good videos in that article posted here for convenience.
