Alcohol inks are so versitile!! You can use them on a felt applicator (or refillable pen) to color metal pieces, glass pieces, plastic pieces, glossy paper, bling etc. Change the color of the whole piece or just accent a section here or there.
You can use them to make cool backgrounds for cards or layouts or mats, or to punch out letters and shapes from.
You can use them to custom color dry glitter. A few drops mixed in white dry glitter will change the color nicely.
I have the Ranger paint palette, but you can use anything non stick really. Place a few drops of each color into its own section and let the ink dry. I have an alcohol ink refillable pen, but you could also use the craft nibs. Anyway-fill up the pen with blending solution (or dip the nibs in it, being sure to soak it). Then use the pen to "wake up" the colors by running the pen through the dried up ink. Then apply it to your project!
The mixatives are waaayyy too cool as well!! The snow cap makes an awesome marble design and the metallics bring a pretty shimmer.
Use them in a ventilated area and don't ever put them in a spray bottle.
For the most part, same general principle as any other ink. As Kim mentioned, you have to use it on nonporous surfaces to get the most out of the effect, which kind of has a stained glass look. If you used regular cardstock, it would just soak into the paper.
Here are some ATCs I made with alcohol ink on acrylic (you can do more than just a splatter effect but I don't have any good photos of examples to show you):