I watched a lot of videos and also read a lot. Stronglifts 5x5 is actually a rip-off from "Staring Strength" so I recommend reading the original book (there's also some videos from the book's author on YouTube).
At first it is very easy to do the exercises in bad form, but as you progress in weights, you will "feel" if you are doing it incorrectly (and probably won't be able to progress much).
For example, as I progressed in squat weights, I started feeling knee pain. This should NEVER happen, if you are feeling knee pain, you are not activating the proper muscles. In general, if you are feeling any pain besides sore muscles, you're probably doing something wrong.
I started doing this program in a normal gym, but the coaches were terrible and couldn't offer any advice besides things like "this exercise is very dangerous, I don't recommend it". Yes, free weight can be dangerous, but it is also the most effective form of workout.
My general advice is: be conscious about form and always visualize in your head what you're going to do before starting a set. Also do regular reviews of your form (ask someone to record you on smartphone).