Run everything in Rosetta 2 on Silicon Mac

1. In Finder, go to /Applications/Utilities/ (or press CMD+Shift+U).

2. Select "Terminal.app"

3. Press CMD+I (capital i) for "Get Info"

4. Check box for "Open using Rosetta"

As shown here:

After that, any process in Terminal will behave as if it is on an Intel Mac. This is the best way to run brew right now, and they have said that there will be a process to move over to ARM when the time comes.

If there are other apps that are compiled for both Apple Silicon and Intel, but you always want to run them under Rosetta, repeat the "Get Info" » "Open in Rosetta" process for each app.