I know that it is only October but if you want to get some great ideas and tips in time to actually make a calendar, you can already start following this "school". I will be posting bits and pieces here until the beginning of December.
This was the first Advent Calendar I made back in 2010 and it is still hanging on our window as a decorative garland. It has moved house with us twice! The hearts are great if you want to hide very small things or love notes. I have used pages from an old Winter season magazine. Below is a tutorial how to fold the heart.