So you buy a nice two shelf bookcase but it’s wobbly and you know it won’t hold much. I’ve recently gotten one and my solution was to put L-brackets on it. After installing about 8 of these brackets at the cojoining parts of the shelving, it is now completely stable and ready for use.
I agree. There are tons of resources out there that will tell you how to do it and typically they come with plenty of comments from other people telling why the particular example is wrong. From there you should be able to piece together a lot of the common mistakes, and understand how not to make them. If you can’t understand the why to any of them, perhaps it isn’t something you should be trying yourself.