If you own "COM", and you notice brands out there with a NET, ORG, IO, CO, XYZ etc, your chances are improved. However, the average user doesn't necessarily think like a domainer and have a "COM is king" mentality (you'd think they should, but you'd be surprised on your hit rate)
You'd be wasting time with anything but "COM". In the past I'll admit I've attempted selling "NET" to internet businesses, who already own their "COM"...absolute waste of time, I failed miserably. If you are to do it, attempt outbounds with "COM", and nothing short of it. IMO
It depends on your target market / end user base, whether it's inbound (inquiries) or outbound (potential beneficiaries of a Web address / Web identiy) domain.