I use the clone stamp and the healing brush A LOT, and one thing I wish someone would have told me is to vary how hard your brush is. Most people leave the clone stamp and the healing brush super soft, maybe thinking that it will blend better, and sometimes that is very true...but a lot of times you'll need to change it to get the best results. There are a couple of ways to change the hardness and I will tell you those here.
I think the easiest way is to right click on the image you're working on with either the clone stamp or healing brush selected. That will open up a dialogue box and one of the options is "hardness". I would love to tell you what to select, but that really depends on what you're doing, so experiment!
You can also click on the brush panel and change the hardness, this will be in different locations depending on how you have your screen set up. If you look all over and don't find it make sure it's visible by clicking Window > Brush (the shortcut is F5).
You really need to play with these settings to get an idea of how they change your clone stamp and healing brush, but you'll get used to it!
Until next time...be Awesome!