With some small bulbs it is difficult to tell which end is which. Do not worry mother nature has taken care of it, the plant's new shoot will always look for the direction of light (warmth). However if you keep to the broad slightly circular side of bulb as the bottom side, you are almost always right.

Put bulbs in an old colander or mesh basket and plant the container straight into the ground. This way you can keep  colors together, Keep the mice away and it makes digging them up at the end of the growing season much easier.