Rule number one of coin collecting is "DON'T CLEAN YOUR COINS." Improper cleaning will reduce the collector value of your coins by 50 percent or more, so don't clean your coins.
There are some very limited things you can do to improve a coin's appearance, but read these instructions very carefully. There are two basic forms of cleaning - Destructive Cleaning, and Nondestructive Cleaning.
Destructive cleaning involves two principal products - those that contain an abrasive, and those that contain an acid. Pencil erasers, Silver or Brass paste polishes ("Brasso"), emery cloth, sand paper and even your fingers represent the abrasive area. Liquid silver cleaner, vinegar, tomato juice, lemon juice, the dips, and soft drinks all contain acids which will damage some, or most coins.
Safe to use as a nondestructive cleaner is a weak solution of pure soap (not detergent) and distilled water. This will remove surface soil, grease and oil, but even this should not be used on proof coins or upper grade copper alloy pieces. After using, rinse very thoroughly in distilled water and allow to air dry, or pat dry. DO NOT RUB. Even a soft cloth will pick up grit and scratch the coin surface, a dead giveaway that the coin has been cleaned.
Above all, avoid the home remedies. Using Tabasco sauce, soda pop or similar products that never were intended for coins is something to avoid. At the same time, don't believe the lurid claims on the labels of the polishes on the market. Despite what they claim, they are not safe for coins and will do irreparable harm to them.