brown sugar. light brown, unless otherwise noted; measurements are always packed
butter. salted, unless otherwise noted
chocolate chips. semisweet and regular size, unless otherwise noted
cocoa powder. natural and unsweetened, unless otherwise noted
eggs. large; do not use different-size eggs for baking
extracts. pure, never imitation
fish. fresh and wild-caught preferred over vacuum-sealed/frozen/farmed
flour. all-purpose and unbleached, unless otherwise noted
measurements. for large measurements, and especially when measuring flour and other powdery ingredients, use a separate spoon to scoop into the measuring cup, then sweep or level the top. Do not tap or press ingredients down except when measuring brown sugar. For small measurements (e.g., 1 tsp. baking soda), use the measuring spoon to scoop and then level off
milk. skim, unless otherwise noted
nuts. raw, unsalted preferred
olive oil. extra virgin, ideally from a dark bottle
salt. iodized table salt, unless otherwise noted
spices and herbs. if not specifically noted as fresh, use dried
warm spices. ground, unless specifically noted as whole
temperatures. always given in degrees Fahrenheit

Because I am a home baker and cook, and I assume you likely are as well, I mainly give measurements in volumes, unless weights (in ounces) are really more appropriate or accurate (as with cheese, and sometimes chocolate).

Always buy the highest quality ingredients you can find/afford, especially with respect to chocolate and dairy products used for baking. For cooking, buy produce in season, and go organic if you can afford it, even if just for a few items each week!