I learn from some digital expert, claim we should apply the sharpening before the noise reduction after color adjustment.
Ok, here's the thing...the OPTIMAL time to do noise reduction is in the same processing pipeline as demosiacing and capture sharpening of the image–meaning the raw processing. So, what that means is to do the global sharpening, image toning and color correction AND the noise reduction ALL in the raw processing pipeline.
OK, in the past some people tended to poo poo the ACR/Lightroom noise reduction–and to a degree, I agree. In the past (operative word "past") Camera Raw and Lightroom's noise reduction was not what most would call "industrial strength".
Andrew (The Digital Dog) and most of the people I know (like Martin Evening, Mac Holbert and even Mike R.) tended to take the REALLY NOISY stuff and do post processing in Noiseware Pro. The problem there was that meant that at best, you only did very, very gentle capture sharpening prior to the noise reduction and all the retouching and other work had to be done AFTER a trip to Photoshop.
So, here's what I would say about "current practice": If your image is from a recent camera and less than ISO 800 and with little Exposure bump in ACR or LR, try your best to achieve the optimal image sharpening and noise reduction settings in ACR or LR. If you often shoot at higher ISO and do post processing exposure bumps, seriously consider doing little sharpening in ACR/LR and take advantage of the power of a 3rd party noise reduction tool.
But know that this is now...and in the future, the "best practice" is bound to change since the tools we are using improve...
BTW, did I mention that the LR 3 beta has some interesting improvements in demosiacing and color noise reduction?
The luminance noise reductions isn't hooked up yet but those practiced in the art of tea leaf reading would probably deduce that LR 3 and ACR 6 would have substantially improved luminance noise reduction that might make 3rd party tools less needed and allow even the HIGH ISO shooter the ability to do both sharpening AND industrial strength noise reduction all in one pass...