In reply to Stone_donkey:
Based on some experience with Canon 350D and 5DMK2 I found it useful to minimise the noise in the source file before it gets to Lightroom. Saving images as raw files will give you more room to manouevre in LR.
Using an iso as low as you dare go is handy - as long as there's light enough to do so.
Then when you take the picture, try "exposing to the right" (lots on Google on this) where you "over" expose the image without blowing the highlights. Check the histogram on the camera to get an indication of how far you can go without losing the bright bits completely.
You'll get less noise by turning down bright bits in LR rather than turning up dark areas, especially on images from older cameras. Shadow areas on my 5D could be shocking sometimes. Newer models won't win so much doing it this way.
Then follow the good advice offered above for any residual noise.