if you are involved in "streetwear", graphic design, making clever stickers, flyers, websites, etc...
here are some examples of mock-logo designs you should NOT do:
zzzzzzzzzzzzzzzzz...

as seen on countless flyers, shirts, websites, etc:

save it for the chinese to bootleg:

don't think this is used that often, but i've seen it enough (simpsons get a pass):

last but not least, you know the deal about polo and rocked back in the day... congrats! move along now:
vol. 2 coming soon...