Jawman,
There have been some excellent responses and tips provided by the many posters. The 4 rules are the very basic and ALWAYS following those 4 to the point it is ingrained in your psyche will prevent any issue from resulting in catastrophic consequences. NRA has the 10 rules of gun safety, and others list as many as 30. Following the 4 will be suffice as a starting point. As others mentioned, proper handling of the guns during all other aspects beyond the firing range are critical and is where other problems arise. In cleaning, storing, transporting you MUST follow the 4 rules each and every time.
For example, when I'm packing up after the range, I clear my guns before storing in the range bag or case. Once I get home and I'm going to put them in the safe, I once again, clear them as they go from range bag to safe. I also do this when removing any gun from the safe, whether to place in range bag or on workbench. Is it excessive and borderline OC? Maybe, but it ensures the gun is unloaded.
Of course the exception is my carry piece which is loaded at all times, unless it's cleaning time or being cleared for a specific purpose.
Above all -- learn the basic safety rules, ingrain them into your conscious actions around firearms AT ALL TIMES. And then, learn to shoot, enjoy, repeat...
EM