Know exactly how and for how long to take the medication - patients need to know whether they are taking a tablet, capsule, liquid, drop, etc. They also need to know the route of administration and how important it is to take the medication at the same time each day. It should not be assumed that patients will understand that which is obvious to you. Anyone who has had a patient put amoxicillin suspension in her child's ear otitis media understands this. It is also important that patients know how long they will need to take the medication.
Some explanation needs to be provided as to why the length of treatment was chosen and is necessary.
Adherence increases when people know why they are doing what they are doing. It includes how disruptive it is to the patient to take the medication, any problems the patient may have with side effects or remembering to take the medication, how dependent on others the illness and its treatment makes the patient, etc. You play an extremely important role in assisting the patient in seeing the value of the treatment both in regard to curing a disease, preventing the illness from progressing, relief of symptoms, improvement in the patient's quality of life, etc. Any factor that you can use to assist the patient in seeing the medication's value will be important. Also, don't underestimate your ability to understand any difficulties the patient may encounter.