The many and varied answers to BOONDOCKSAINT's question are a testament to solo divers' thoughtfulness, thoroughness, and ingenuity. As always, I am able to glean new insight from reading these many posts.
I would like to add that as a current "solo" scuba diver and a former senior skydiving instructor (Instr. "A" & "B") I am a firm believer in ALL types of redundancy - equipment and training (really important to have a backup chute and to be able to REACT without conscious thought). To that end, it is my personal belief that all the equipment and training we accumulate, utilize, and confabulate about might as well rust and fade away in the corner of our garages...unless we continually practice all the skills we have learned. IMHO this entails repetitive rehearsal of locating and using all the equipment we normally bring on our dives, as well as donning and doffing (no cheating-keep the gloves on) B.C.'s, mask(s), fins, tools, etc. Also, although it might seem simplistic or silly, or even highly improbable, consideration might be given to odd scenarios which can occur - loss of lights or computer info (even backups). Disorientation. Panic -- ever spit your reg out accidently when you were a "newbie" solo diver? People do it !!
I guess my not-so-succinct point is that "Murphy" has a nasty way of sneaking up on you, plus -- as we are all aware -- problems only seem to multiply once they begin in the underwater setting!! However, through vigilance and "real-world" practice we can both mitigate these factors and show the rest of the diving community that we are serious about our highly skilled and fascinating aspect of this sport.
Hope this isn't too off topic. Just a thought or two...