Openly ogle other opportunities
We like to convince ourselves that the job market as fair as any other market. The laws of supply and demand ensure that we will always end up in the correct position for our skills and talents, right? Unfortunately, we don't usually act like we know we could do better.
Seeking new employment is a good way to communicate to your current employer that you're sick of them and want a change. You can be direct and open about this, staing plainly that you're dissatisfied and discussing your options for advancement inside the company, or you can be subtle, and leave your résumé in the print tray for your boss to find, or your computer turned on and logged into a job-listings board. You can even use a company phone to schedule meetings with headhunters, ensuring that your co-workers overhear you when you do.
Even if you don't find anywhere new to go, your restlessness is bound to begin to rub off on everyone else at the office. This will doubtless clue your bosses into your intent to flee, and they will likely try to preempt any serious damage by terminating you before you have a chance to secure a position with their competitors and copy the corporate contacts directory.