If you're going to make cocktails you need to consider your tools. Stirred drinks? Take mixing glasses. This isn't just a regular piped glass, this is tempered glass, because as you go to work making your drinks, if you shake them or stir them too hard, you're likely to break something. A regular piped glass that's not even tempered is going to break more easily. When you're putting ice in there, you're changing the temperature of this glass a lot, and the faster your thermal changes occur, the more likely weak glass is to break, so look for tempered glass. It's readily available in a lot of homewares stores, but be sure to ask.
A mixing spoon is a wonderful thing. It has a bowl for making measurements. Whenever you see a bar spoon measurement, it's usually about this, about an eighth of an ounce when you flatten it out. The twisted spoon helps move the ice around in the glass, and the flat end can be used to pick ice depending on how you need it. It also can be used to crack ice if you want to move your drinks along quickly, and slide it back out.
When you finish your drinks, they finish cooking in the glass or finish being shaken in the tin, you have your strainers. This is a julep strainer. It's circular and it's perforated. It fits nicely inside the mixing glass, and it will hold ice back so you can let your spirit flow comfortably without getting any cracked or whole ice cubes into the drink.
This is a Hawthorne strainer. You can tell by the spring around the outside. It fits on top of the mixing tin nicely. Push it closed so you make sure you don't have any of your ice chips falling out around the side, and you do your pouring like that.
This is an English-style shaker, which is to say it's metal on both sides. It's different from a Boston-style shaker, which would be a pint glass, well a slightly smaller pint glass, plus this.
These tools right here are the essentials and the basics in making a good cocktail, whether it's stirred or shaken.
An incredibly important tools, especially if you're following your recipes, are going to be your jiggers. We see 2 ounces, 1 ounce, three-quarters, one and a half, half and a whole. Whenever you see these in recipes they are generally meant to be followed. If you've worked long enough with pour spouts or just have a good sense for how much is coming out of the bottle, you don't really need them, but I strongly suggest jiggers, both for the amateur and for the hurried professional on the go.
Your jiggers are going to help you get a consistent drink every time so you'll consistently have half an ounce, 1 ounce, every time you pour. There are different schools of thought as to how far you fill the jigger. You can get a flat pour like this, and that's a meniscus, where you see the actual meniscus forming over the top of the jigger. Different recipes may call for different amounts, so you always want to be sure if it's a shy half, a full half, what have you, but the jigger gives you a tool by which you can measure how much is going into your drink and consistently make your drinks every time.
These are some of the tools you can use to make a good, consistent cocktail.