There’s a Tumblr site called American Drink that I highly recommend. They’ve just posted an article on basic bar tools that is pretty much spot on—it reminds me to get a long spoon. I have one exception to their advice, though, and that is use two metal cups when shaking drinks. A very heavy pint glass may work just fine as the second cup, but it’s heavy. Heavy glass is safer glass, though. To get rid of the weight and increase the safety of vigorously shaking a liquid in two cups, I always recommend a true set of what I just found out are called French shakers. A plastic top cup will work, too, but ice will scratch it, and fats from cream or milk will stain it. Stainless steel cups will last damn near forever.
But the constant reminder to find a good restaurant supply house or second-hand store is both necessary and overlooked. There is no reason to spend good money on tools that look good, but probably won’t last a single night of heavy cocktail production.