How to build an overfitted network in order to increase performances I am learning how to implement CNN, and searching on the internet I have found that a trick to design a good network is to first build it in such a way that it overfits, and then use regularization to elimnate overfitting and have a good performing network. 

But how do I do this? I don't understand how do I build a network that overfits on purpose? And also in which way do I use regularization after?

Can someone helo me?

Thanks in advance.
The reason of overfitting is generally because of the high(unnecessary) complexity model. So if you train a too complex(large) model, you will get a high training accuracy and low test set accuracy. Then you can start to fight with overfitting  with getting more data, dropout, regularization, early stopping, global average pooling, feature scale clipping or dropping some of layers from your network.