I think the library may have a few books on invisibility. But blending in with your surroundings works if you can work with meditation, which isn't a literal invisibility but more like being overlooked. There are other books on more magical methods of invisibility but I haven't bothered to practice them, something about a mist veil and Greek mythology.
If you happen to have the chance of playing games based on stealth, perhaps hide-and-seek or paintball, these would be great opportunities to practice. Practicing in public is more difficult because people in stores more likely ignore you than not see you, or even try to make themselves invisible to you so to speak. Avoiding drug addicts that beg in front of stores is hard mode, slipping past them means you did it.