Shooting black and white can be tricky, the things to look out for are contrast, brightness and texture. When you're looking at a colour photograph, your eyes would most likely be drawn to a subject that has contrasting colours against the background. (imagine a big red hot air balloon on a green field).
But in monochrome photograph, the red and green colours might have the same brightness, therefore resulting in a monochrome photograph that looks flat without the colour contrast.
As a general rule always try to adjust the brightness of different colours separately to create more contrast, in other words adjust some colours darker and others brighter so there is a noticeable contrast between the subject and the background. There are always exceptions, it all depends on what you want to achieve with the monochrome photograph.
Windows light are great for creating better light contrasts, place your subject near to a window on a bright sunny afternoon and include a wide range of greys in the frame, example the singlet and furniture. Shadows also helps to achieve wider greys, try using flash to throw highlights over certain areas of the frame, you might be surprised with the results.
Patterns in an image can be interesting on a monochrome photograph, if the above image is in colour your attention might not be drawn to patterns, but in black and white the patterns are far more compelling.
Tell me whether the first thing you noticed in the photo above is actually the pattern on the girl's untied neck ribbon?