I think the only way to give a generic answer is to do a general adjustment on a complete image. If you are trying to modify the red of a strawberry on a white background, you have to retouch the strawberry, there is no other option. The following example is a global change. I chose a photo where the reds do not predominate as flat solid elements but are details to highlight.
At first glance, the remarkable "reds" are those of the model's sweater, lips, and hat. The background also has some reddish spots, I take them as secondary since they are not the main objective in this case. Maybe a few strands of hair from the reflection of the sun
The complementary color to red is green. In an RGB image from an image editing program, it would correspond to the green channel. Working in Photoshop, if I load the green channel as a selection and invert it, I get the reds in the photo.
From here, you can work in several ways, in this example, one of the most subtle adjustments is to apply an adjustment layer, like a red photo filter (in the image at 50%)
This allows you to work with different elements until you get the effect you want depending on the type of image, such as changing the opacity and mode of the adjustment layer and/or changing the levels of the filter mask. In the image below Overlay mode opacity 50%:
To clip and increase the effect to only a part of the image, like the model in the example, change the mask levels and hide the part of the mask that is not relevant:
How to get a more vibrant red?
In the image below there is a color scheme with a red accent. The black background is the one that offers the greatest contrast due to the property of black that magnifies the intensity of all colors. But where red vibrates the most is with its complementary: cyan-blues.
In the example image, by inverting the red filter mask selection and applying a cyan or blue photo filter, the reds will be more intense