A nice summary of techniques, though they charge:
Accelerated Learning & Memory Improvement at Memletics.com - helping you learn faster
Harry Lorayne is good at teaching pneumonic devices.
Evelyn Wood is famous for her speed reading techniques.
You can reduce math mistakes by simply looking at the mistakes, figuring out what the psychological cause was, and devising a system to outo-check or auto-correct yourself.
All of these things take work, and deteriote if not practiced.