A useful set of articles and tutorials from IBM about domain, crossover domain, lookup, value list.
Adding a valuelist (ALN Domain) in Maximo
Adding Lookup Functionality to a Field in Maximo
Setting Up Crossover Functionality in Maximo
Filtering an out of the box lookup in Maximo
Troubleshooting Crossover Domains
Setting Up A Conditional Domain
Associating Lookups in Maximo using the MAXLOOKUPMAP Table
Conditional Lookup Functionality
Displaying Additional Information Through a Relationship in Maximo
Limiting Lookups using WHERECLAUSE
The Hidden Feature of Crossover DomainLabels: beginner, domain, lookup