Displaying things that you have stories behind or that you have collected is an ideal way to start a conversation. The key is organization, keeping similar items together and keeping them in odd numbers.
You can either organize items by size, or to be artful, mix the sizes up.
Make your colors match! If you have a white collection, place them against a dark background. Collections of a lot of color should go against a neutral background.
If you have bookcases with little to put in them in terms of books, but do have a collection with nowhere to put it, place them into the shelves next to the books, but be sure to make sure that the books will not fall over and damage them and that the books themselves are organized by size and color if possible. Make sure sequential series go in order! Your guests will now not only be looking at your collection, but at your books as well!
Place delicate items out of reach, but in a safe spot, you want to display your collection, not risk its demise!