Discursive writing is a very tricky art, as many Higher pupils have discovered. I would always recommend students read the comments section of broadsheet newspapers, many of which are available for free online and provide a broad range of styles and opinions.
Recently, I came across these clips on Youtube, which demonstrate the art of putting forward a strong personal argument. You can see how each argument has a strong bias but tries to disarm the opinions of those who disagree with them. Be warned, though, this is complex stuff and may be, at times, difficult to follow.
You can begin here then follow the subsequent parts 2, 3, 4 and 5 which are displayed in the right hand menu.