Interestingly, some of the highest-achieving pilots seem to place soaring safety above all other issues. They are likely to quote things like 'It is better to be on the ground wishing you were in the air, than in the air wishing you were on the ground.'
That's a reference to judging conditions, which brings me to a neat little list of the 3 methods for ensuring your personal safety.
On that first point, it takes years to get a good grasp of micro-meteorology. I can remember being at a slope soaring site and an instructor said 'better take off soon, this sea breeze will die shortly.' Sure enough, less than 40 minutes later, no more sea breeze, no more flying. I was most impressed!
I guess the lesson is, learn all you can from people familiar with the sites you fly from. Gradually build up your knowledge of how to analyze conditions. These days there are plenty of other resources available too, books and DVDs. Among other things, they cover soaring safety issues.
On the second point, flying technique, again it takes a while. Tens of hours to really get the hang of doing things well, preferably with plenty of take-offs and landings which tend to be the trickiest. Paragliding is a judgement sport like no other, and if you don't do it you lose it.
Like any sort of flying, there is an intensive period of training where hours matter, but after a point, when you are competent, what matters most is your currency. That is, when you last flew and how frequently you fly.
The most active pilots are the most skilled pilots in general. Assuming good 'pilot attitude', a skilled pilot is also better at the safety aspects than a rusty one.
The third point, about being cautious, should be easy. It's just a decision really, isn't it! But I guess there are some hot-heads out there... Everyone has a different personality, so some pilots might have to work a bit harder at being cautious, for their own good.
To give a bit of 'edge' to this point, consider a whole bunch of paragliders on one little ridge, or perhaps in one narrow thermal. A reckless pilot, someone without caution, would be a soaring safety hazard in these situations! A huge potential there for injury.
Reminds me of some video footage I downloaded off the Net a few weeks ago. Some nutcase was doing a spiral dive very close to another paraglider. He managed to collect the other guy's wing and they both ended up throwing their reserve 'chutes as they plunged towards the ground in a tangled mess!