Memory cards are relatively expensive so it pays to buy the largest capacity cards you can afford, as the price per Mb will drop significantly compared to lower capacity cards. Shop around for the best prices.
Memory cards can sustain wide variations in temperature but do not leave them in direct sunlight. Beware of condensation when coming in from the cold and always keep cards in their protective cases when not in use. Keep cards away from magnetic fields. Electrical contacts in some cards are vulnerable since they are openly exposed. Never touch them to avoid failure or loss of image data.
When using a Microdrive in your camera, first check there is an eject switch as the drive has no lip to remove it from the memory slot in your camera. Not every camera that accepts a Microdrive will function properly with it. Some cannot stand its higher operating temperatures and power requirements, so check with your manufacturer before buying one. Microdrives are susceptible to humidity and large variations in temperature can cause reading or writing errors. Do not drop them as their moving parts may get damaged.