Scrub with a toothbursh or get a specialist tongue cleaner. Depending on the nature of the spots on the tongue, it can indicate poor general health or infections like Syphilis.
According to webmd, black tongue or hairy tongue can be caused by antibiotics. I would call your doctor on Monday for any advise he/she might be able to give. It said it's not a serious condition and...
You don't mention your ethnicity, but we commonly see harmless melanin (the substance that produces a brown color to the skin) pigmentation of the fungiform papillae (which are the larger "taste...