I don't fancy myself as an expert in this stuff, but I have some tips.
First - Pencil, various Brushes and Zoom are your friends and are very useful for making empty eyes - just fill 'white' spots in eyes with color.
Second - Lasso Selection is much better than Freeform Path in terms of selecting, let's say, eyes. After that just Ctrl-C + Ctrl-V them as another layer and do whatever you want.
Third - Basic glowing is applied through Right-Clicking on layer and choosing Blending Options. There are a lot of stuff there, but in low-level manipping Outer Glow, Inner Glow, Color Overlay and Gradient Overlay are the most useful.
Fourth - It's a good idea to google a Heart-Pack for your Custom-Shape tool, so you would be able to do more... let's say, artistic heart-eyes.
Fifth - Google how to create a Fog Brush and use it if you want to add some steam or gas.
Sixth - Glowing is your friend, especially Outer Glow, when you are adding captions. It makes text much easier to read.
Seventh - You can add extra-space for big captions by using Canvas Size in Image.
Eighth - Spot-Healing Tool is very useful to covering app minor mistakes or removing censoring. But be careful with it.
Everything else could be googled when you'll need it.
Good luck.