Choosing lenses for Nikon D90?

I'm choosing between a nikon d90 with 18-105mm lens alone or with 18-55 and 55-200 together
what should i choose?

It depends what do you like to photograph

The single solution lens would be the 18-200 mm lens.

Just make sure that you buy Nikkor AF, AF-I or AF-S lenses if you want to shoot with auto-focus all the time

If I had a do over it would be the 18-200 Nikkor. I do enjoy the 18-105 a lot and have printed up to 30x40 inch prints off the D90/18-105 combo. My next lens will be the 80-200 f2.8 not the 55-200.
Hope that helps.

In choosing a new lens you should ask your self - what kind of pictures am I NOT getting now, and what lens will help me get them?
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As said here, the 18~200 is a killer "walk around lens" of reasonable good quality, good wide angle, semi-good telephoto (be nice to be 300mm tho) and with the image stabilization, helps on the telephoto part as well as lower light. It has a rather close focus ability and the 3.5 to 5.4 f/stops at wide open are of no problem out here in the desert land of forever sun. Auto focus is… OK, but other lenses are faster. As said, as a all purpose "do almost anything" lens for having on the camera all the time until a specialty lens or a prime is needed, it can't be topped.
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I have had one since 05 or 06 now and it has been through hell, however, Nikon engineering comes through again and it works fine (it and my camera ride in a saddle bag or trunk on my HD all over Arizona and the southwest).