Ive been playing terraria on the PC for 10 hours total now and I still have not found a magic mirror! Any idea how i can increase my chance of finding one?
Magic Mirror usually appears in Gold Chests in the underground. Gold chests also have a higher spawn rate inside underground houses. If you have yet to find a magic mirror, you may simply be having bad luck, since the chests' contents are random.
The quickest way to get a magic mirror may be to roam the undergound and loot all chests you may find and hope for a magic mirror to be there.
I typically use a map viewer program such as MoreTerra to find particular items.
This program can help you find ores, specific items in chests, or particular map features. Depending on how much you know, this may contain spoilers about upcoming features of the map that you may want to discover for yourself.
Depending on how you feel about third-party programs and map viewers, this may be considered a form of "cheating". Personally, after 10 hours without a magic mirror, I would use a map viewer, but that's my patience level.
Gamer15's response is outdated. This can sometimes happen pre-1.2, but not any longer. Chests in the Ocean only spawn with specific items; the Magic Mirror is not included in the loot table.
I would suggest what others have said, just generate a new world. It'll be easier to find one that way.
Someone I know had this problem, they pestered me until I finally gave in and handed one over, so maybe ask a friend who also plays terraria, and if that fails try to use a combo of spelunker and teleportation potions to explore unexplored areas. Also, when searching try to prioritize going to ice caves, because in regular underground a magic mirror has a chance to spawn in a gold chest as the "rare" item, but in ice chests you can find an ice mirror AND one of the "rare" items, so it not only is faster but contains more yield.