Sweet spot of the 18-105 lens?

After lot of reading of this forum, I have lately bought a D5000 with 18-105 lens.
I am (still) a noob in the DSLR world but I want/try to learn a lot.

Those of you who use this lens, could you please tell me where are the sweet ranges of this lense?

Like: Which zoom range is recommended to use for best sharpness, or which ranges to avoid if possible. Same with f numbers (aperture).

Thank you for your help, comments.