Before 2010 the ticker (trading) symbols for US options typically looked like this: IBMAF. This consisted of a root symbol ('IBM') + month code ('A') + strike price code ('F'). The root symbol is the symbol of the stock on the stock exchange. After this comes the month code, A-L mean January–December calls, M-X mean January–December puts. The strike price code is a letter corresponding with a certain strike price (which letter corresponds with which strike price depends on the stock).
On February 12, 2010 the five-character ticker format stopped being used in the US and Canada.
The new standard is now fully in place, as in the first few months after February 12 the LEAP roots and additional roots needed to handle large amounts of options for a given issuer were consolidated into a single root ticker for a given underlying symbol. Options Clearing Corporation's Options Symbology Initiative (OSI) mandated an industry-wide change to a new option symbol structure, resulting in option symbols up to 23 characters in length. March 2010 - May 2010 was the symbol consolidation period in which all outgoing option roots will be replaced with the underlying stock symbol.
On March 18, 2013, CBOE Mini Options became available for trading on a select group of securities (AMZN, AAPL, GOOG, GLD, and SPY). These options represent a deliverable of 10 shares of an underlying security, whereas standard equity options represent a deliverable of 100 shares. CBOE appended a "7" to the end of the security symbol to represent the mini option contracts.
The OCC Option Symbol
The new OCC option symbol consists of 4 parts
1. the root symbol of the underlying stock or ETF, padded with spaces to 6 characters
2. the expiration date, 6 digits in the format yymmdd
3. option type, either P or C, for put or call
4. strike price, as the price x 1000, front padded with 0s to 8 digits
SPX 141122P00019500 is a put on SPX, expiring on 11/22/2014, with a dollar strike of 19 and decimal strike of 5 ($19.50)
LAMR 150117C00052500 is a call on LAMR, expiring on 1/17/2015, with a dollar strike of 52 and a decimal strike of 5 ($52.50) 
Mini-options contracts trade under a different trading symbol than standard-sized options contracts. Mini-options carry the number "7" at the end of the security symbol. For example, the Apple mini-options symbol is AAPL7.
AAPL7131101C00470000 is a Mini call option (10 shares) on AAPL, with a strike price of $470, expiring on Nov 1, 2013
AAPL131101C00470000 is the standard call option (100 shares), with the same strike and expiration date.