An implementation intention is a plan of how to implement a particular habit.

Cues can have a very wide range of forms. The two most common are time and location. Implementation intentions leverage both of these. The format is "When x arises, I will perform response y." Studies have shown that implementation intentions are effective: they increase the odds of sticking with habits. Voter turnout can be increased by forcing people to create them. People who make a specific plan for where and when they will perform a new habit are more likely to follow through. Telling yourself "I am going to be healthier" without making a concrete plan will not be as effective. People may think they lack motivation, but they may really lack clarity. Once the implementation intention is set, you do not need to wait for the right moment. Simply follow your predetermined plan.

I will x [behavior] at y [time] in z [location]
I will meditate for 1 minute at 7 am in my kitchen.
I will exercise for 1 hour at 5 pm in my local gym.

Another benefit is that it can help you to say no to things that will pull you off course. If you have vague dreams, you can rationalize little exceptions all day long and not see the actual things you need to do to succeed. You want to get the urge to do the right thing at the right time even if you do not remember why. You might start to get antsy around the time of day you do not work out if you do not go the gym, for example.

The Dittero effect: obtaining a new possession often creates a spiral of consumption that leads to additional purchases. Many human behaviors follow a similar pattern where the next action follows naturally from the last action. The previous action was the cue. Identify a current habit, and then stack a new behavior after. It is a special form of an implementation intention. Pair the new habit with an existing habit. This can be used to design an obvious cue for any habit.

After current habit x, I will new habit y.
After I pour my cup of coffee, I will meditate for 1 minute.

The key is to tie your desired behavior into something you already do each day. Then you can take advantage of the natural momentum, like a positive version of the Dittero effect. You can also insert new behaviors into the middle of current routines. For example, place a book on your pillow between getting out of bed and going into the shower. The key is selecting the right cue to kick off the behavior. Brainstorm and search for the best place to insert new behaviors into your lifestyle.

Habit stacking works best when the cue is highly specific and immediately actionable. The more tightly bound the habit to a specific cue, the more likely you are to act. Remember the first law is to make it obvious. Implementation intentions and habit stacking are strategies to make it obvious.