Design for the production process early
If the part will eventually be molded or stamped, design for that process from the beginning even while prototyping in machining or additive. Retrofitting draft, uniform walls or die-friendly geometry late is expensive.
Decide when tooling is justified
Compare the cumulative cost of machined or printed parts against tooling plus piece price at your realistic annual volume. Bridge tooling is a legitimate middle step when forecasts are uncertain.
Qualification and first articles
Define what constitutes an acceptable first article before the tool is cut. Ambiguity here turns into weeks of argument at exactly the moment your schedule has none left.
Supplier scaling
Confirm your supplier's capacity at production volume, or plan the handoff to a production supplier while the prototype shop is still engaged. Doing this deliberately beats discovering it at launch.