The Opening-Meld Requirement
Why People Get This Wrong
People often assume that once a player starts making combinations with tiles already laid out on the table, they can't add to their initial meld anymore. But actually, the opening-meld requirement means you must start by placing your own tiles in valid groups or runs before you can manipulate existing ones - it's not an all-or-nothing deal where you're locked into that initial setup once started.
Official Verdict
Each player must make an initial meld before manipulating combinations already on the table. The initial meld consists of one or more valid groups or runs placed from that player’s rack during a single turn.