When I first started squatting, I looked like a newborn giraffe that was using their legs for the first time. I made a lot of mistakes. It took me a year of lifting to finally get comfortable with squatting, and figuring out what works and what doesn't. One big issue I had with squats (and deadlifts too) was that my knees would cave in. It didn't matter if the weight was easy to lift, my knees wanted to meet. Also, it's important to note that most beginner lifters with have many things wrong with their squats, including caving knees. Anyway, my teammates worked diligently with me to correct my form. Here's some things I've learned...
Push Your Knees Out
You want to consciously think about the movements. As you squat, put your knees out. This also creates a habit of really thinking about everything your boding is doing. Although squatting is a natural movement, there's a lot that goes into it. A good squatter thinks about everything -- about the steps taken on the platform to how tightly they grip the barbell.
Play With Stance Width
Although there may be suggested stance widths, you can actually play around with that. Personally, when I moved my stance closer, I saw a huge improvement in my squats. Not only did I minimize the knee cave, I was able to perform just a much better squat.
These can help you train your body to push your knees out. I'd suggest not doing these with weights. All you need is yourself and a band.