When parents stop by my room to ask me a question, I usually find myself reaching for a post-it note to write down my contact information. Then, usually I see them later and hear that they lost the post-it and if I could give them the information again. Thanks to technology there is something that can help when those important post-its go missing.
You can create QR codes that are embedded with whatever information you want, such as your contact information. One of my favorite QR site is http://goqr.me/, it is super easy to use. Just enter in your information and Ta-Da! So now you can create a QR code with your contact information and tape it to your door. Since most people have smart phones, they can scan it and the information will be automatically in their phone for them to save. You may still have to use your post-its, but hopefully not as many