The New Debugger
Starting with version NW 7.0 EHP2, SAP introduced the New Debugger which is much more powerful than its predecessor the Classic Debugger. One may find this New Debugger overwhelming and be tempted to stay with the old one, but it is very important not to let go and to take it slowly, especially since the Classic Debugger becomes obsolete in NW 7.5.
Here is a series of articles introducing the New Debugger. It is recommended that you practice a little bit between each article to make it your own and not get discouraged by the profusion of new features.
Introduction to the New Debugger :
Advanced features :