Baking time: keep in mind that all ovens and pans are different, even if they look the same or very similar. The baking time in my recipes is as accurate as it can be, but it might take you more or less time. You can use a thermometer that is placed inside the oven (like the OXO oven thermometer) to check that your oven is at the right temperature. I recommend you keep track of how your oven works and what tiny details you might need to adjust. 

Mint chips: I used Guittard green mint chips and love them. Another brand is Mint chocolate chips from Olive Nation and also Andes Creme de Menthe chips.

Mint extract: I use peppermint extract and it's usually Simply Organic peppermint extract or Pure peppermint extract from Mc Cormick. There are others, like Wilton's Pure peppermint baking extract or this Mint chocolate chip extract from LorAnn that I never tried but am very intrigued by.

Chocolate chips: semisweet are the best and my favorite brands are Guittard's Semisweet baking chips and Ghirardelli semisweet premium baking chocolate chips. But any brand you normally use works just fine!

Green color: if you want to color the cookie dough (I never do), you can use green food coloring such as Americolor soft gel food color or Wilton leaf green icing color. Start with a very small amount, like a drop or two, and see how it goes. You can always add more but not substract. 

Size: you can make any size of cookies you want. For larger cookies you need some extra minutes in the oven and the yield will be lower. For smaller cookies it's the opposite, less baking time and more cookies.

Freezing: the unbaked dough can be stored in the freezer: scoop the portions on the baking sheets (without touching but no need to leave much space between them) and freeze the pan until the dough is rock solid. Transfer them to airtight bags so you can remove the baking sheet from the freezer and use less space to store the pieces of dough. Bake directly, without thawing.