While the basic desires of ABDLs are simple, a wide range of practices and a large body of how-to knowledge have developed. While there are some important points (this first section), neither ABDLs nor non-ABDLs are expected to know all the details. Specific FAQs are available for parents.
Briefly put, the superset of ABDL practices includes anything diaper-related, anything babies or children might enjoy, anything adults might enjoy, and some details that are necessary since ABDLs aren't real kids. However, it is unlikely that any particular ABDL will enjoy all of these.
An ABDL's process of learning what he enjoys may be a lifelong journey. (While not all ABDLs are men, we'll use the male pronoun for brevity.) Binge-purge cycles might be a problem early in this journey, and later on, habituation might be a problem. About halfSTATS of all ABDLs go through binge-purge cycles, which can be troubling and costly if not properly managed. Later, as the ABDL becomes more experienced, habituation will occur. Habituation causes the newness of repeated activities to fade. While ABDLs should be open to trying new things, they should be aware that they won't stay new.
The best way for someone else to learn about the interests of any particular ABDL is to ask him. The ABDL and his partner will need to communicate their desires and boundaries. This process is called "negotiation." It should take place before roleplay and in a mature headspaceDEF. In addition to the more pleasant details of checking and changing, the partners should discuss elements of their biology or past that can flare up during roleplay, commonly called "landmines." They also need to maintain balance in the relationship as a whole, compromising so that the needs of both partners are met in a way that will last for the long-term. Unlike a chronological baby, the adult baby won't outgrow diapers and/or babyhood.
Since these details are things chronological babies wouldn't be concerned with, they are easily overlooked. However, they can prevent long-term stability and happiness if overlooked. With them out of the way, we can briefly touch on some of the more enjoyable ABDL practices. Below is a more detailed but incomplete summary of the interests of the ABDL community. Most individuals would be interested in some but not all of them. Generally, those who are strictly adult babies will emphasize roleplay and babyhood, while those who are strictly diaper lovers engage in them. However, many ABDLs aren't strictly one or the other, but a mix of bothSTATS.