You can use any container--I like the idea of a glass jar so I can see the contents, but a shoebox or coffee can would work just as well. Decorate the container however you wish. I used scrapbook stickers of words such as "laughter" "blessings" and "memories". I was going to put 2015 on it, but decided against it so that I can use the jar every year.
I will put small mementos in the jar all year long--ticket stubs, trinkets, etc.
I also have a small note pad with colorful patterns, and will write out memories with the date. By 12-31-2015, there should be lots of items in the jar and Dave and I can look back on our year and remember all of the fun we had.
These make great gifts, too!