Here are some very generic (and paraphrased) notes from a short talk today, by Deepankar Sharma.

1. Whenever you release a new major version, make sure you keep a copy of the whole “ecosystem” to be able to run it whenever you want. At any point in time, you should be able to run any version of your software.
2. When writing benchmarks/tests/etc., try and ensure that you cover a broad spectrum of test data, to try and replicate the different types of data that users could possibly have.
3. Don’t develop applications with modes. Be very careful before you add a new mode to your application, effectively adding one more code path to maintain.
4. (Bonus) Beware of too much extensibility