So 15 years ago when you wanted to jazz up a photo or make it stand out it's because you had a few dozen filters on your camera or you had the pleasure of developing your own film. Now with the advent of hundreds of photo apps and software like photoshop or paint shop pro to name a few we are able to do just this in seconds and minutes.
With photoshop you can apply one of the many filters or actions to quickly adjust a picture to give it a sepia tone or ancient or 80's feel which is if course wonderful.
I myself am a fan of adding little effects and some basic brush effects on photos.
Here is where I have an issue. When people change people so much that they remove freckles or change the position of eye brows, neck lines or slim waist lines.
I believe that thru photoshop we have lost some of what used to make photographers really strive to get the picture right the first time. At times there are exceptions to the fact, you can lighten a scar or lighten teeth, but many times the people are already fine the way they are.
The only times I usually touch up someone to that point is when asked. I will ask when I shoot a wedding if there's anything the couple would like fixed that's not too invasive. Often times I adjust people's teeth or bags under their eyes and basic blemishes. I never move locations of facial features. I have been asked to slim a waist line before but only of asked.
When working with skin I usually try to keep a natural look. I work with layers a bit in photoshop to achieve this. There are dozens of examples on how to work with skin online so I won't touch upon that right now. I have never liked the plastic look to skin that some photographers like to bestow upon their subjects. I like to look at it like this, my photo is not an ad for Guess Jeans and won't be appearing on any billboards. You can spend 30 minutes on a picture trying to get someone's skin perfect and make them look almost alien or you can keep it somewhat natural.
When using effects or presets or actions I like to try and treat it like going out to eat, I don't do it too often and I don't order everything on the menu. I always see photographers posting on facebook and can almost instantly recognize their work by the different effects they apply. I also judge them by the creativity of the effect, most times if I can figure out what they did in 10 seconds I'm not impressed. If an effect can add mood or depth to a photo then by all means. There's no set rules in photography only guidelines.
So it's always up to you how you retouching your photos. My only advice out of all this is concentrate on the photography end of it not the retouching. Amazing photographer is nicer to hear than amazing photoshopper.