Write bulkified Apex trigger logic that processes up to 200 records per transaction without hitting SOQL or DML governor limits

In-depth guide

Steps

1. Collect all record IDs from Trigger.new into a Set<Id> before making any SOQL queries, then issue a single query with a WHERE Id IN :idSet clause outside any loop
2. Build Map<Id, SObject> lookups from query results so you can access related data per record in O(1) without nested queries
3. Accumulate all records requiring DML into a List<SObject> or List<SObject> update list inside the loop, then perform a single DML statement after the loop completes
4. For cross-object field updates initiated by a trigger, query parent or child records in a single batch query before the processing loop begins
5. Use Limits.getQueries() and Limits.getLimitQueries() for diagnostic logging during development to catch limit approach early
6. Test with a data factory that inserts 200 records in a single DML call to verify the trigger stays within limits at maximum batch size