You can lead a lavish lifestyle and bill it to the company. That will result in excessive G&A. Sometimes the company's filings on SEDAR will show how much it spent on travel, entertainment, etc.
Other things will also result in excessive G&A. If the company is spending lots of money on stock promotion, then it will show up in G&A.
2- The problem with mining stocks is that:
A- Many are overvalued.
B- The majority are run by a (part-time) CEO who is trying to enrich him/herself at the expense of shareholders.
C- Almost everybody is inflating their technical reports.
D- Some management teams choose to do crazy things.
A longer post on what I think about mining:
http://wp.me/p1mOGr-BZ