Training birds, or any animal for that matter, can be done by essentially anyone who's willing to put in the time but there's a few things that many people tend to overlook.  The difference between a trusting, responsive bird and one who may learn slowly or only preform under certain circumstances lies in these fine details.

Motivation

 Motivation is how much the bird desires to work for you, whether you use a primary motivator (food) or a secondary motivator (stimulation) your bird has to be motivated to work for it!  This typically means reducing those motivators from their every day lives and using them solely for training.

If you're using physical touch or a toy as a motivator this means letting the bird play with the toy less so they look forwards to playing with it during training.

For food, it can be a little more complicated depending on how you do it.

 The preferred method of food reward if to just alter the feeding schedule, do training first and feed meals afterwards, I wouldn't be interested in working for cake if I just had a three course meal, would you?  I prefer this method because it's safer, you don't risk lowering their body weight or making them ill.  The most common method used is weight management, reducing up to 5% of the bird's regular meal and filling that 5% with treats during training.  Using the weight management method requires careful attention paid to their weight through weighing them daily and recording their weights, ensuring the weigh does not drop below 5% it's original weight and definitely no lower than 10% as that risks serious health issues.  I don't like this method because of these risks but for some birds, they will just continually eat and gain weight which puts them at risk of other health issues (like fatty liver disease) at which point that method becomes necessary to allow the bird to stay at a healthy weight and train effectively.

Behaviour and Communication

 Watching your bird's body language and how you are able to communicate with the bird is the only way you'll be able to teach a concept, if neither of you know what the other is saying you will get nowhere!

If your bird is starting to play more than it wants to train, is looking around, chewing the perch, and overall seeming disinterested, that's you bird telling you that they don't want to do this anymore and it's time to end the session before they get grumpy.  If you're trying to teach a trick that involved being in close proximity to your bird and they're starting to nibble your hands or show defensive behaviours, that's them telling you that they aren't ready to move that far yet and you need to back up and slow down the process until they're ready for you to get that close.  Pushing a bird past these obvious lines of communication will more than likely result with them flying away or just biting you.

Along with you understanding how to read the bird the bird needs to understand how to read you.  How do you accomplish this?  Start off with basic concepts like target training and clicker recognition, these simple things allow the bird to understand how to do something for a reward, they start to acknowledge your body language and how it's directing them to preform and action and will help them know when they've done something right as well as how that progresses in to a larger concept.

 A consistent bridging device is the best way to communicate a correct behaviour to your bird.  A bridging device is a word or sound that can be repeated consistently and is always followed by some form of positive reinforcer (food, stimulation, etc.).  Consistency is important, if you make a different sound every time the bird does something right they will struggle to understand what marks the correct behaviour.  A bridging device must sound at the exact moment the bird did the correct behaviour, this helps the bird pinpoint exactly what they did correctly and increases the odds of them repeating that behaviour.  If you're making a different sound every time they will not know what your bridging device is and won't think they've done something right until they've got the treat in their mouths, this can mean that them standing around or reaching for the treat (whatever they were doing when being rewarded) is the behaviour they will believe they did correctly and is the behaviour they will repeat.

Rewards and Jackpots

 This is by far one of the most helpful things when training a bird, if a bird doesn't like what they're being given they won't work for it, if they have the same thing every day they'll get bored of it, a key to a good reward is variety in substance and quantity.

Establish what your bird loves best, many birds change their favourite foods around frequently so it's important to note when they start to lose motivation for the reward you are using and change it up. Good food reinforcers include hulled sunflower seeds, millet, banana chips, oat groats, anything that can be consumed rapidly so they don't forget what they just did to earn the food, a good stimulative reinforcer may be a favourite toy, sounds, or physical touch.

Simple enough, but what's a jackpot?  A jackpot is something you reward the bird with when they've made a larger step in the right direction, anything that's better than what you're already feeding them (this can mean more of the same treat or just a better treat in general).  A jackpot helps the bird understand that what they just did was better than what they were doing before and increases the odds of them repeating that behaviour to earn the jackpot again.  An example of this would be: If I'm teaching a bird to step up and they're just leaning over my hand, all I'm rewarding with is millet then suddenly they put a foot on my hand I'm going to reward with something better, like sunflower seeds, the bird will want more of those sunflower seeds and start to put their foot on my hand more frequently to earn them.

Session Length, Session Frequency and Ending the Session

 Birds all have different attention spans, it's important to watch their body language for signs of boredom and lack of interest.  If you push a bird past their reasonable limit they will lose interest in training all together and may learn to hate training!  The average training session should not go any longer than 15 minutes, when just starting out many birds will only be motivated long enough to work for 5 minutes.

The more sessions you have the faster the bird will understand this concept, this is true but there's also a risk of overdoing it and stretching the bird's attention span too far causing them to regress.  According to the various CPBT-KA's (certified professional bird trainers, knowledge assessed) the best number of sessions to have for one concept in one day is 2, one in the morning and one in the evening.  Some birds are equipped to handle three sessions, some can only handle one, you have to evaluate your bird and determine what works best for them.

How you end the session is important, you always have to end on a positive note so the bird looks forwards to coming back the next day.  If you end with the bird tired, overworked, frustrated and confused, they won't want to work with you and will refuse any attempts by you to get them to participate.  Have the bird enjoy the session and end it as soon as you see them getting bored.

Positive and Negative Reinforcement

 The two most common methods that work best with birds are positive reinforcement and negative punishment (not to be mistaken with negative reinforcement and positive punishment ).  Positive reinforcement is the action of encouraging repetition of a behaviour through some form of reward, negative punishment is discouraging the repetition of a behaviour by removing something positive from the environment.  

An example of positive reinforcement: The bird lifts it's foot on to my hand, I reward it with food, the bird wants to earn more of that food so it will look to repeat the behaviour of putting it's foot on my hand

An example of negative punishment: The bird starts to nibble at my hands instead of stepping up, I slowly move my hands away and pause, removing the opportunity to earn the desired reward.  The bird doesn't want the opportunity to earn a reward taken away, the bird will reduce repetition of nibbling on my hands in order to continue earning treats.

Negative punishment is not the same as positive punishment, we are not harming the bird in any way or initiating a negative response from them.  Positive punishment has been linked to numerous behaviour problems including feather destruction, screaming and aggression. Birds can not correlate an action with positive punishment and understand that their action caused the punishment, positive punishment causes regression and emotional harm to the bird. Do not use positive punishment on a bird.

Progression

 How quickly you pace sessions is determined by the bird,  when teaching a concept you have to break it down in to steps so it is easily understood.  These small steps are extremely significant, birds who learn behaviours by jumping right to the end behaviours commonly forget what they learn and the entire concept must be relearned from scratch.  When taught through a variety of smaller steps a bird may forget different steps and only have to be retaught a few of those last steps to accomplish the end behaviour, the constant repetition displayed through smaller steps also solidifies the concept in their brain and makes it harder to forget.

How many steps you need is dependant on your bird, if you make too many steps and the bird is jumping ahead of you the bird may become frustrated and confused, it's your job to keep up with the bird's pace.  If you have too little steps and the bird is stuck it's your job to break it down in to smaller steps so the bird can accomplish the end goal.

It's long, I know, but incorporating all of the things listed above can drastically improve not only the bird's ability to learn and responsiveness but also the bond and communications you are able to have with your parrot.  It might seem like a lot at first but it's really worth it to see just how excited they can be to work with you, training has become my girls' favourite part of the day and it's obvious to me just how much more they enjoy my interaction after working to connect, communicate and bond with them through training.