This is especially useful if you are just staring at your image and you are not sure how to edit it, this is a really easy way to instantly figure out the direction to go with your photos.
All you need is to take your image in photoshop and add 4 adjustment layers ontop, there are other ways to achieve the same results but this is by far the simplest one.
With your base image all you need to do is to add 3 base adjustments and one artistic, don´t worry if it looks weird at first, at the end you will adjust the opacity of the layers until the result looks pleasing.
First add a curves adjustment layer and set the Preset to medium contrast
Next add a Photo filter adjustment layer and set it to a warming filter if your base image already is cool or a cooling filter if your base image has warmer tones.
Then add a a vibrance adjustment layer and drag up both vibrance and saturation, just remember to always have less saturation adjustment than vibrance, don´t worry if it looks weird.
Finally add a HUE/Saturation layer and adjust HUE up and down to any color you find interesting.
Now make all except the first adjustment layer invisible and adjust the opacity of that layer until the image looks pleasing, make the next visible and adjust the opacity of that one until the image looks good, work your way through all layers.
Each adjustment by itself can look quite bad, but with a little bit of each layer combined you can quickly achieve great results.
This is a really good and simple technique to use anytime you are somewhat stuck with your images.