Application Design

Hi,
I'm only a novice in java,VB.net and SQL but I've gotten to the stage where I'm starting to look at the actual design of an application. Are there any web sites that list some sort of usability guidelines for applications or maybe analysis of effective or ineffective design? Someone has mentioned common conceptual models to me as well, but I have no idea what that is. I've tried google to no avail. Are there certain guidelines that say the file, edit bar are always on top, etc?

At the moment the applications I'm creating, just follow the look of what I can remember of applications I've used. I'd just wondering if there's some sort of guidlines or such?

thanks,
D