Great cookies start with great ingredients, so don't be cheap with your choice of chocolate. If you can't find high-quality chocolate chips at the grocery store, buy a bar of chocolate and chop it up yourself. When it comes to the type, you can't go wrong with semisweet chocolate chips or chocolate bars with 50-60% cacao. Unless you're in the mood for a slightly more sophisticated taste, in which case you can go for bittersweet chocolate with 70% cacao or more.