We all collect bits and pieces on our travels, and they can look really good in a well-built curio cabinet.
The Basic Design
You need to know how deep it needs to be, how high and how long. You will also need to work out the size of glass you need for the doors and the number of shelves. A good wood to use is oak, because it is a fine-grained hardwood and can be worked easily.
Cut the Various Parts and Finish Them
Cut the two sides for the cabinet and the top and bottom, and ensure that they are exactly the right size. The two sides must be identical lengths as must the top and bottom. Likewise the shelves must all be the same size and the tops and bottoms of the doors.
Assemble the Cabinet
Spend a little time to work out the best way to join the pieces together. The frame could benefit from dovetail joins, or you could use wooden doweling to create a feature with the doweling ends. The door frame should have mitered joints, with the glass held in place by removable strips in case it ever needs replacing. It's also important that the shelves are fitted so they're perfectly horizontal.
There are many variations on the basic model curio cabinet and only your imagination will limit your final design.