If you shoot raw, can you preview the image on the LCD of your camera?
All digital photos start out as raw data.
If you are "shooting JPEG" the camera converts the raw data to a viewable image before storing it on the memory card. If you are "shooting raw" the camera saves the raw data to the memory card. But the camera also processes the raw data and creates a jpeg preview image and attaches it to the raw file. When you look at the picture on your camera's LCD screen that is almost always what you are viewing - the jpeg preview image.
You can't really view a RAW image, because a RAW file is not much of a viewable image. It is a set of linear monochrome luminance values that has not had gamma correction, other light curves, demosaicing, etc. applied. When the data is converted to RGB using demosaicing certain settings such as gamma, contrast, color balance and temperature, saturation, etc. are applied.
... isn't it hard to determine whether you shot a good picture?
Even when you look at the jpeg thumbnail/preview image on your camera's LCD it is often hard to tell if you shot a good picture. The screen is much lower resolution than your image. The brightness may be adjusted too bright or too dim. The color may not be accurate and is probably not adjusted to compensate for the ambient lighting where you are viewing it.
You are much better off learning to use the histogram (also drawn from the JPEG preview) to judge exposure rather than looking at the brightness of the LCD screen. A perfectly exposed image can look grossly overexposed if the LCD screen is at the brightest setting when you are in a darker environment. It can also look very dark when you are viewing it in very bright light.
The LCD display on the back of your camera is designed to make every picture you take look as good as it possibly can. In other words, it lies like a politician! If you are viewing a 25 MP image on a 1MP screen it means that each pixel on the screen is displaying a combined 5X5 pixel area of the original image. Your focus could be blurred by as much as the width of four pixels and you wouldn't be able to tell a difference from a perfectly sharp image! Likewise, the color and contrast are rendered in a way that the manufacturer thinks is most pleasing to the most potential buyers. If the preview picture on the LCD screen reduced contrast enough to display the entire dynamic range of the RAW file, no one who buys a camera based on how the picture they just took in the crappy light of the store looks on the back of the screen would ever leave the store with one.