It's not hard to do, you can calibrate just about any monitor, some laptop's can be difficult though. You can buy a calibration tool that comes bundled with calibration software or at the very least you can use photoshop's Adobe Gamma or freeware on the web to try and get close to calibrated. The most common reason for a gallery to be deleted is that it's too dark, most of the time it's because the photographer is toning their images on a monitor that's way too bright.
I use GretagMcBeth's ( Xrite ) Eye one Match 3 software with the Eye-One Display 2 colorimeter (Xrite link), but there are several units available that work just as well. Here's a review by an online printer of several different calibration tools:
And here's a tool recommended by a couple of MaxPreps shooters here in WA, the Pantone Huey
a good inexpensive alternative.
Compared to the cost of most digital photo equipment, calibration tools are pretty inexpensive. If you're going to spend thousands on the latest bodies and the fastest glass, then why process your images on an uncalibrated monitor? You want your work to look it's best, that's not going to happen if you don't control every aspect of the creation of that image. If you don't have a calibrated monitor then you're simply guessing when you process your images.
I calibrate once a week, but for most shooters once a month is sufficient.
Here's another article on the web that talks about monitors and calibration and also compares some of the calibration tools available. Smartshooter.com