I pick up shells when I go to the shore and I follow the same steps each time.
1. Pick up all the shells or pebbles that interest you.
2. Sit crossed-legged on the sand (very important) and sort through the pile, making two catagories: Maybe and No.
3. Discard the No pile.
4. Take another look through the Maybe's and only pick out the prettiest, most interesting shells or pebbles.
5. Make up your mind. You are only allowed to take one home to add to your collection.
6. Go home, put the new shell in your jar and wonder about all the ones you had to leave behind.