The answers to these questions should point you in the right direction for database selection. After this, you can issue a regular search statement in the usual format. If you use qualifiers or f ield codes you may need to OR them together to make sure that a particular feature is covered in all your selected files. The system responds with a list of the file banners for the selected databases and then the usual prompt for a search statement. The search loo ks exactly like one run in a single file, though the postings will be for the whole group together.
Duplicate records are common in multi-file searches.
Controlled vocabularies vary among files as will the availabilty of additional indexes. Prefer natural language terms linked by proximity operators, because controlled vocabulary will vary. Use truncation to cover variant word forms and English versus American spellings. Be particularly careful with classification numbers and prefix codes, as different fields may need to be ORed together to make sure that all files are covered. Watch truncation, a little goes a long way.