BTW, I typically edit with picmonkey.com-- it may sound funny but this website has many photoshop actions ( good for people like me who can't spend 500 bucks on photoshop!)
1. Don't over Saturate!
This is one of the most important editing "don'ts" in my opinion. A common mistake is to snap a photograph and then turn up the color. This will give you red/pink faces, will turn whites into purples, etc. A good solution is to put the saturation at the lowest setting, then crank it up SLOWLY. This way you can see that there is a significant difference in the color without making it look like a messy rainbow.
2. Black and Whites Must Be Done Right!
Instead of clicking the " black and white" button, select the sepia tool. Then pull it all the way down to the corner. This will make a "warmer" black and white, without looking so typical. I personally am a big fan of black and whites, don't get me wrong, I just think that a little variety is good. And it really depends on the image as well . A brighter portrait image, for example, will look beautiful in a light, classic black and white. And even dark images can look beautiful with a dramatic black and white. Oh and while on the subject-- NEVER use straight out sepia. The auto sepia tone is much to yellow. If you do, pull it to a more gray tone. Sepia is becoming a bit outdated ;-)
3. Easy With the "Dark Edges"
A favorite tool for many people while editing is the dark edges tool. For a while it was OK, but now it seems like everyone uses it. If you're going to do dark edges, fan them out a little larger and fade them a bit.
( please excuse the pic quality, these pics below were taken from a tiny sample pic on my website so they are a little blurry)
4. Avoid White Edges
While we are on the topic of edges.. try to avoid white. Or any other color for that matter. They can make a picture look pretty tacky. In general, stick with darkened edges, or none at all.
5. Don't Soften Entire Images!
A common mistake is to soften an entire image. If you are planning on softening picture, at least select a section to keep sharp-- a face usually, or a small object like a ring. Generally, I think it looks better to just let your camera take care of the blurring and it will usually give you a lovely depth of field.
6. Be Nice to Your Contrast
Contrast is super valuable. However... it is SUPER important not to over contrast an image. Below I have an exaggerated example-- just so that you can get the idea for what I am talking about
Hope these tips help! Have a great evening :-)