8. Not accepting that someone else may be better at solving your problem than you are - Okay, this final entry is a two-part item that I admit I threw in here for my own benefit as well as yours. Even so, troubleshooting problems can be a daunting task, not to mention a time consuming one!
Part I: Sometimes you simply have to throw in the towel and call a support rep at the software or hardware vendor to get a problem solved. After all, it's their product and the issue you're having might be quite easy for them to diagnose (and possibly even repair). Many times this can be done simply by upgrading from the software or firmware version you are on to one that has already been released to address your particular issue. This is valuable because it could potentially save you hours (or worse, days) of troubleshooting and diagnostics.
Part II: If, after performing Part I, the support rep tells you its something on your end and not theirs, accept that they have a pretty good chance of being right. After all, they likely deal with many different hardware and software configurations, not just yours. Don't hinder their progress in helping you resolve an issue because you "checked all that" first. Instead, accept help from anyone that is willing to assist, especially the experts who only deal with their own products!