Photos often look duller on screen than the scene did in person. A modest adjustment usually closes that gap.
Flat photos usually lack separation between light and dark, not colour. Raising contrast often makes an image look more colourful than raising saturation does, and it looks natural rather than processed.
Skin is where oversaturation gets caught. Landscapes tolerate a lot of extra colour, faces do not, and a portrait pushed too far goes orange in a way everyone notices and nobody can name.
Judge it away from the sliders. Move the adjustment, look at something else for a moment, then look back. Eyes adapt quickly and it is easy to keep pushing past the point where it stopped looking good.
A little goes a long way. A saturation of 110 to 130 percent usually looks rich, and above 160 colours start to look unnatural, especially skin, which turns orange. Make small moves and compare with the original.
The Punchy preset is a ready made mix of stronger contrast and colour, and it is a good place to start before you fine tune. If the picture looks fake, back off the saturation first, since it is the setting most easily overdone.
Usually too much saturation. Try backing it off and raising contrast instead.
This editor processes the first selected image. Save it, then repeat with the next photo using the same settings.
No.
It raises contrast and colour together, giving a stronger, more vivid look. You can then adjust the individual sliders from there.