Unsharp pictures result from either out-of-focus or motion blur. We can start with the focus since that is what you mention.
Starting in (P)rogram mode (green P), put the camera into AF-S focus mode (single servo). (page 35 of the PDF manual.) Set the focus area to "single" (page 38). Using the 4-way rocker switch on the back, pick a focus point to use (for example, the center one). Put your chosen focus point on the subject. Half press the shutter release to activate the focus. When focus has been achieved, the camera will beep. Gently press the shutter release all the way down to take the picture.
If you are using a VR lens (for example, your 18-200mm) you may need to wait an extra half second during the focus lock for the VR to finish its job.
---------+---------+---------+---------+ Joseph K Seattle, WA, USA