2012: My personal jQuery plugin starter template...

jquery.plugin.1.0.0.js

/**
 * jQuery pluginName
 *
 * @author    First Last
 * @link      http://site.com
 * @docs      http://github.com/username/pluginName
 * @copyright Copyright (c) YYYY First Last.
 * @license   Dual licensed under the MIT and GPL licenses.
 * @version   1.0.0
 * @date      YYYY/MM/DD
 */

//----------------------------------

// Notes to self:
//console.profile('profile foo');
// ... code here ...
//console.profileEnd('profile foo');
// ... or:
// console.time('timing foo');
// ... code here ...
// console.timeEnd('timing foo');

//----------------------------------

;(function($) {
	
	'$:nomunge'; // Used by YUI compressor.
	
	//--------------------------------------------------------------------------
	//
	// Constants:
	//
	//--------------------------------------------------------------------------
	
	/**
	 * Commonly used variables.
	 *
	 * @const
	 * @return {boolean} Description goes here.
	 */
	
	var constants = {
		
		NS     : 'pluginName',                                       // Namespace identifier.
		PREFIX : 'pn',                                               // Class prefix.
		C      : ((typeof(console) !== 'undefined') ? true : false), // Check if the javascript console is available.
		
	}, // constants
	
	//--------------------------------------------------------------------------
	//
	// Public methods:
	//
	//--------------------------------------------------------------------------
	
	methods = {
		
		/**
		 * Init constructor.
		 */
		
		init: function(opts) {
			
			//----------------------------------
			// Loop & return each "this":
			//----------------------------------
			
			return this.each(function() {
				
				//----------------------------------
				// Local variable(s):
				//----------------------------------
				
				var _   = $(this),                                                          // Target object.
				data    = _.data(constants.NS),                                             // Namespace instance data.
				options = $.extend({}, settings.external, $.fn[constants.NS].defaults, opts); // Merge settings, defaults and options.
				
				//----------------------------------
				// Initialize data:
				//----------------------------------
				
				if ( ! data) {
					
					//----------------------------------
					// Setup variables (for examle):
					//----------------------------------
					
					//var $divs = _.children('li').children('div');
					
					//----------------------------------
					// Namespaced instance data:
					//----------------------------------
					
					_.data(constants.NS, {
						
						target  : _,
						options : options,
						//divs   : $divs,
						init    : false
						
					});
					data = _.data(constants.NS); // Make it easy for the rest of init().
					
				}
				
				//----------------------------------
				// Data initialization check:
				//----------------------------------
				
				if ( ! data.init) {
					
					//----------------------------------
					// Data initialization flag:
					//----------------------------------
					
					data.init = true;
					
					//----------------------------------
					// Do stuff here:
					//----------------------------------
					
					// .. rest of init ...
					
					methods.foo.call(_); // Example of calling foo() where "this" === $(this).
					
					var foo = bar.call(_, data); // Example of calling bar() where "this" === $(this) and data is passed parameter.
					
					baz.call(_); // Example of calling baz() where "this" === $(this).
					
					$.fn[constants.NS].example.call(_); // Example of calling secondary function where "this" === $(this).
					
					// More stuff here. Don't forget about callbacks:
					
					//----------------------------------
					// Callback:
					//----------------------------------
					
					options.onAfterInit.call(_);
					
				} else {
					
					if (constants.C) console.warn(constants.NS, 'already initialized on', this);
					
					return this;
					
				}
				
			});
			
		}, // init()
		
		//--------------------------------------------------------------------
		
		/**
		 * Foo test.
		 */
		
		foo: function(elem) {
			
			//----------------------------------
			// Handle API invoked method:
			//----------------------------------
			
			if (typeof(elem) === 'undefined') elem = this;
			
			//----------------------------------
			// Loop & return each "this":
			//----------------------------------
			
			return elem.each(function() {
				
				//----------------------------------
				// Local variable(s):
				//----------------------------------
				
				var $$  = $(this),
				data    = $$.data(constants.NS),
				options = data.options;
				
				//----------------------------------
				// Stuff here:
				//----------------------------------
				
				// ...
				
			});
			
		}, // foo()
		
		//--------------------------------------------------------------------
		
		/**
		 * Removes plugin from element.
		 */
		
		destroy: function() {
			
			//----------------------------------
			// Loop & return each "this":
			//----------------------------------
			
			return this.each(function() {
				
				//----------------------------------
				// Local variable(s):
				//----------------------------------
				
				var $$ = $(this);
				
				if ($$.data(constants.NS)) {
					
					// Destroy!
					
				} else {
					
					if (constants.C) console.warn(constants.NS, 'already initialized on', this);
					
				}
			
			});
			
		} // foo()
		
	}, // methods
	
	//--------------------------------------------------------------------------
	//
	// Private methods:
	//
	//--------------------------------------------------------------------------
	
	/**
	 * About this function here.
	 *
	 * @this   <object> ($(document), for example)
	 * @return <void>
	 */
	
	bar = function(data) {
		
		// ...
		
	}, // bar()
	
	//--------------------------------------------------------------------
	
	baz = function() {
		
		// ...
		
	}; // baz()
	
	//--------------------------------------------------------------------------
	//
	// Method calling logic:
	//
	//--------------------------------------------------------------------------
	
	/**
	 * Boilerplate plugin logic.
	 *
	 * @link http://docs.jquery.com/Plugins/Authoring
	 * @constructor
	 */
	
	$.fn[constants.NS] = function(method) {
		
		//----------------------------------
		// Boilerplate:
		//----------------------------------
		
		if (methods[method]) {
			
			return methods[method].apply(this, Array.prototype.slice.call(arguments, 1));
			
		} else if (typeof method === 'object' || !method) {
			
			return methods.init.apply(this, arguments);
			
		} else {
			
			$.error('Method ' + method + ' does not exist on jQuery.' + constants.NS); // Should I override? http://api.jquery.com/jQuery.error/
			
		}
		
	}; // constructor()
	
	//--------------------------------------------------------------------------
	//
	// Public access to secondary functions:
	// http://www.learningjquery.com/2007/10/a-plugin-development-pattern
	// http://stackoverflow.com/questions/11286312/superfish-plugin-fn-extend-how-does-this-code-work
	//
	//--------------------------------------------------------------------------
	
	/**
	 * Just an example.
	 */
	
	$.fn[constants.NS].example = function() {
		
		//----------------------------------
		// Loop & return each "this":
		//----------------------------------
		
		return this.each(function() {
			
			//----------------------------------
			// Local variable(s):
			//----------------------------------
			
			var $$  = $(this),
			data    = $$.data(constants.NS),
			options = data.options;
			
			//----------------------------------
			// Logic here...
			//----------------------------------
			
			// Example of calling a public method:
			methods.foo.call($$); // $.fn[constants.NS]('open', $$);
			
		});
		
	}; // example()
	
	//--------------------------------------------------------------------------
	//
	// Default settings:
	//
	//--------------------------------------------------------------------------
	
	var settings = {}; // Initialize config object.
	
	//----------------------------------
	
	/**
	 * Private settings.
	 */
	
	settings.internal = {
		
		// ...
		
	}; // settings.internal
	
	//----------------------------------
	
	/**
	 * Public settings.
	 */
	
	settings.external = {
		
		// ...
		onAfterInit : function() {} // After plugin initialization.
		// ...
		
	}; // settings.external
	
	//----------------------------------
	
	$.fn[constants.NS].defaults = settings.external; // http://stackoverflow.com/questions/11306375/plugin-authoring-how-to-allow-myplugin-defaults-key-value
	
})(jQuery);

Based on jQuery's plugin guidelines found here.

Note to self:

/**
 * @see http://stackoverflow.com/a/920322/922323
 */

$.fn.pluginName.exists = function() {

    return ( !! this.length);

};

Put inside plugin and call like so:

$('#foo').pluginName.exists()