You cannot make a photograph "stands out (w/out being artificial)" if the picture itself is taken on a cloudy / dull day. I supposed you are familiar with PS; so the basic adjustments using levels &/or contrast for a start for the overall pic involved. It should, at least, bring out the full dynamic range of the said picture.
For more fine tuning, you have to dabble with curves.
You will have more leeway if your photograph was taken in the "RAW" format but nothing beats maximizing the situation at hand when taking the pic at the point of time (ie, setting the right in-camera settings - contrast, WB, etc).
I'm not saying there's anything wrong with your equipment or software. Just the lighting condition... you obviously have no idea what I'm talking about, or how levels work. Pls read up AFTER you get advice... if not how r u gonna improve?
Shooting on cloudy days often causes colour to wash out, creating a hazy grey cast over the images. The creates problems with the tonality of the image...
Tonality is the range btw a pure black pixel and a pure white pixel in simplified layman terms, FYI.
Also, if you really want help, post the picture in question up. We're commenting based on what you say, which I realise may not be accurate since descriptions aren't always very specific.
Cloudy day means that the overall ambient colour temperature may not be 6500k but 7500 or even 8000+. This cool cast can be compensated by either adding a warming filter to your shots or doing the WB manaully on your camera (if it has that function).