When it comes to getting sharp well focused images, the most important thing you need to know is having a fast aperture. So, the aperture is shown on most lenses either on the body near the focal length (Nikon) or near on the ring around the front of the lens (Canon). The smaller the aperture number, the smaller your depth of field will be. Also, the more sharp your focus will be. So, having a lens that has a 1.4, 1.8, 2, or 2.8 are considered to be better lenses, because they usually help with having tack sharp images and make it easier to shoot in low light situations.
My favorite lens in my bag right now, is my 50 mm 1.8 lens. This lens is great for getting tack sharp portraits and also really good shooting in lower light situations like weddings, or concerts. The downside to lenses with aperture sizes of 1.4, 1.8, 2, or 2.8, is they are often expensive... However, some are pretty decently priced. My 50 mm Nikkor 1.8 lens wasn't that expensive and often times you can find aftermarket lenses that are 1.8 or 2.8 that are decently priced and will still produce great images.
Moral of the story is great glass (lenses) is more important then the camera itself. Most photographers will tell you when looking at buying equipment, you should invest in glass, glass, glass!!! To give you an idea of a great set of lenses and the cost, if you were to get a 14-24mm 2.8, and 24-70mm 2.8 and a 70-200mm 2.8, you would be looking at around $6000 for the Nikkor or Nikon made lenses. But, that set up will be great for any situation!