Answering my main question "How do I know which parameters how to tweak?"
While the design of the input and output layers of a neural network is often straightforward, there can be quite an art to the design of the hidden layers. In particular, it's not possible to sum up the design process for the hidden layers with a few simple rules of thumb. Instead, neural networks researchers have developed many design heuristics for the hidden layers, which help people get the behaviour they want out of their nets. For example, such heuristics can be used to help determine how to trade off the number of hidden layers against the time required to train the network. We'll meet several such design heuristics later in this book.
Learn Which Parameter How to set
Training a neural network means
what parameters should the have at the edges in order to model our data well.
My question being answered here. Yeah! Make sure to have read (at least the first chapter) of the book mentioned above. Then you will understand what is talked about in this video!