Methods and Tools
The methods or tools you choose are less important than the fairness and consistency with which you apply them. Dogs can be trained by giving or withholding rewards or corrections. The best trainers have an understanding of all these methods and will use them in varying amounts to obtain optimal results.
When choosing tools or methods, look to the dog as your guide. As with rewards, it's the dog who gets to decide what it finds most aversive. For example, many people assume that a citronella collar or ultrasonic collar will be more humane or less aversive than a traditional "shock" anti-bark collar. This is probably because people generally like the smell of citrus emitted by a citronella collar, or can only hear a lower pitched beep and not the piercing ultrasonic tone of the ultrasonic collar. Maybe they've had the unpleasant experience of putting their finger in an electrical socket as a child, or associate "shock" with "shock treatments" or "the electric chair."
The reality is that many dogs find the strong citronella scent or the piercing ultrasonic tone to be extremely aversive. My own dogs are absolutely terrified when the low-battery warning begins to beep on our carbon monoxide detector, and one of them flees the room when an orange is peeled. In addition, the citronella spray and ultrasonic tone are not adjustable to the dog's temperament and sensitivity, whereas all modern "shock" type collars have a variety of levels which enable you to use the mildest correction that is still effective.
The same rules apply for other training tools. A prong collar looks like a torture device but is often more easily tolerated by the dog than an itchy or restrictive halti or Gentle Leader. Some dogs are crushed by a stern word, while others will look at you with a smile and a wagging tail. Some will stop in their tracks at the mere sight of a squirt bottle, and others think biting the spray of water is a fun game.
The bottom line is that any tool can be used humanely, and any tool can be abused. Rather than obsessing over tools and methods, consider this: Are you happy with the results of your training? Has the dog's quality of life improved due to the training? Does the dog have more freedom and privileges than he did before the training? Are you able to take him more places with less worry? Does the dog seem to like you? Does the dog seem to fear you? Are you embarrassed by the dog's behavior? Are you afraid to take the dog out in public? Are you proud of the dog's accomplishments? Your answers to these questions will help you to determine if your current training plan is working.