Characteristics of this type of shot: flower fills the frame; the background is out of focus; contrasting colors; visual interest through composition.
Shoot with a zoom lensuse your longest zoom to get in tight and get the flower to fill the frame. This was shot with a 200mm lens, and the flower was actually a few feet away in a garden.
Shoot at flower level. Set up your tripod so you are level with the flower (remember, don't shoot down on flowers), which requires you to squat down (knee pads are great for getting shots like thisI wish I had remembered mine that day).
Shoot in aperture priority mode and use the smallest number f-stop your lens will allow (in this case, on this particular lens, it was f/5.6) to keep the flower in focus but the background out of focus.
Now, bee patient (okay, that was lame). Actually, I saw bees flying around from flower to flower, so I sat there with my camera focused on the flower until a bee actually landed on the flower. Then all I had to do was press the shutter button.
The shot was taken in natural light, but it looks fairly soft because the sun had tucked behind some white fluffy clouds, which are great for flower shots because it diffuses the harsh direct light. I didn't set up my tripod until the sun actually went into a large bank of clouds, so patience (for the right light, and for the bee to land) pays off.