Olympus e620 Lens help

[droidz]

Hey guys, I saw around the forums some people doing really nice Macrophotography, and I was wondering about a few things:

1, which lens for my camera would be good to do Macro?
2, I have a 40-150mm lens, would that suffice? Although, when I do closeups with this lens, the image never focuses properly for me =|

thanks!