Follow the below link, read it, consume it, grok it.
2009 CWE/SANS Top 25 Most Dangerous Programming Errors (If it doesn’t come up be patient. It looks like the server is getting hit pretty hard with bloggers like myself linking to it.)
On a side note, now that the holidays have calmed down I’ve been working on a series of “Often Unused Operators” like ~ and |=. Credit goes to Jeff Clark for turning me onto this. Hopefully I’ll have the first one up on Friday.