If you shot a whole series of wedding or event photos using natural light at high ISO settings, this could be a very useful tip. Use Lightroom's Auto Import feature to add a pre-set to all the images as they're imported.

First, you have to make the pre-set. Start by looking through your library for shots you've already made that are typical of what you might shoot at this ISO. If you don't find any, take a couple of friends into an interior that has lighting similar to what you'd have to be shooting for. Deliberately shoot some shots at each of your three or four highest possible ISO settings (the ones wherein you know that there will always be more noise that is acceptable to your standards).

Put those found or created shots into Lightroom and move through the images with Info turned on (press I until you see the ISO in the Info). When you see an image that's representative of the type of image you want to clean up and that shows the ISO you want to create the preset for, follow this routine for cleaning up noise: Press D to go to the Develop Module and then open the Detail panel. Zoom to 100% so you can see the "grain" easily. Drag the Luminance slider to the right until you've eliminated as much noise as you can. Drag the Color slider to the right to see if you can improve the situation even more.

Since reducing noise usually softens the image and reduces detail, you'll want to recover as much of that detail as you can with the following sharpening routine: In the Sharpening sub-panel, start with the bottom slider and work your way to the top. Press the Opt/Alt key and drag the Masking slider to the right until the white spaces cover only those edges your really want to sharpen...otherwise, you'll re-introduce noise back into the image. When you've got that down, use the Opt/Alt key to show you the areas that will be affected by each of those sliders. When you release the Opt/Alt key, you'll see what you've done to the image. You will have also maximized sharpening of the most important edges while leaving alone most of the areas where the most pixel noise was introduced.

Once you've done the Noise Reduction and the Sharpening for that ISO and subject type, create a new Develop Preset. To do that, be sure you're in the Develop module. Open the Presets panel and click the + icon. In the resultant dialog, shown below, turn off all the adjustments except Noise Reduction and Sharpening.

Then save the Preset in a Camera Settings folder as Camera Name Serial # ISO 6400 (or whatever it was).

If you've shot a whole card at the ISO whose noise level you want to correct, you can just apply that present to the entire collection on Import.

When you bring home a shoot in which that ISO has been used for only some of the images that were downloaded, start by going through the shoot looking for that ISO and type the number of the Color Label you want to assign to that ISO. When you’ve assigned all those, click that color label in the Filters bar of the Toolbar. You'll then have nothing but frames shot at that ISO, so do a Select All, press D for Develop Mode, open the Presets panel, and click the Noise Reduction preset you've made for that ISO. Bingo! They're all as fixed as they're likely to get.

If you don't feel that Photoshop Lightroom's current (and much-improved) noise reduction does the job as a plug-in you love, you could process your best images on one of those. While you've still got that Color Label selected, right click and choose Edit in Photoshop to edit a few selected images in Photoshop and then use an Action or Droplet to cause the noise filter of your choice (e.g. Noise Ninja) to auto-correct all those images again.