Kevin Schroeder makes a suggestion to all of the Magento developers out there - be sure to know your indexes and how to use them to your advantage.
When I first got into Magento development, in my mind, there were two ways of getting data from the database. You would either call Mage::getModel(‘catalog/product’)->load($id) or you would work with the collection. If you wanted to get a filtered list of something you would use the ORM to get it. But as I’ve gained more experience (fairly quickly, I might add) I realized that there was more to the puzzle. A good portion of this is because I work with Magento ECG and some of the best Magento devs and architects can be found there and I’m a quick learner.
He gives an example of going beyond the usual one-to-one relationship most people use with Magento's models. He includes an example of wanting to fetch a list of all products in the same category as another and the "anit-pattern" that comes with it. Instead he offers the solution of an index, a simple one that merges the catalog category and product index ID. This makes using a custom query with a handy join much easier and much faster.