All depends what look you like I suppose, I rarely touch sharpening myself
If you like landscapes, meybe try watching videos on using filters, removing objects, dropping in new skies etc
If it's portraits, try skin softening, eye highlighting, blemish removal, levels
Theres all sorts of filters, layers, and general image manipulation for different tasks, all you need is a bit of imagination, practice, and watch "how to" videos
I enjoy creative live, so when their photoshop week was on, I watched a lot, then bought the course. I think its superb, but cant find the time to watch/practice as often as I'd like
Some tutorials on youtube are excellent too
The best thing about this way, is, for me, I can watch a wee bit over, then try, then re-watch if needed