I'm always dissecting “looks” that I see in photos, and I've seen this one for a while now. I named it Wedding Day because that's mostly what I see the effect used on – wedding photos shot outdoors in the afternoon. It's got a very subtle warm-reddish look to it with a slight vignette. After playing with a bunch of sliders, I settled upon some white balance changes as well as some changes in the Split Toning panel. It's also got some changes to Vibrance and Saturation for a slightly desaturated look. It sounds like a lot, but I think the effect is pretty subtle overall (at least compared to some of my other presets). Also, while it's named Wedding Day, you'll see in the sample below that it works just fine on non-couple photos too
Once you apply it, you can tweak the look by changing your Tint and Temperature sliders (move Tint to the right for more red). And of course the overall Exposure will change the look too. I find it works well with a slightly darker overall exposure and if your photo isn't too warm to start with (if it's already a warm photo, the preset tends to make the skin too red – in which case, just move Temp/Tint sliders to the left).
1) Unzip the preset zip file on to your desktop
2) Go to the Develop module. NOTE: YOU MUST BE IN THE DEVELOP MODULE
3) Go to the Presets panel on the left. Right click anywhere in it and choose “Import”.
4) Select the .lrtemplate files you unzipped in Step 1 and click Import NOTE: DO NOT IMPORT THE ZIP FILE