To lash safely and effectively you need to consider the layout of your working area, your storage and what equipment you will need. Some sort of bed or couch is a must but you will also need to think about client comfort. You can always add padding or towels to make it more comfortable. Your clients will be laying there a long time and if they get uncomfortable they will fidget and this will make your job so much harder. Ergonomic lash pillows can be a great help. Not only do they support your client's head but the sides can be used like a shelf where you can place your products.
Good lighting is essential. You need to be able to see clearly as some of those lashes are tiny! Good lighting will prevent you from straining your eyes. With volume you need to focus more as you are attaching the lash and a poor light source is going to make it difficult and can cause your eyes to ache. I use Glamcor lighting as I find it the most effective. There are various settings and the adjustable arms allow you to work on an area that's clearly lit up from multiple angles. Ring lights are also gaining in popularity.
The music is primarily for your client but plays a role in making your job easier. The music you choose will depend on your tastes but I would recommend that it's not something too upbeat. You want your client to relax so you can work without fluttery lids. It is important to note that you will need a music license unless you choose to play music that has no copyright.
This will vary depending on your setup. I find a tall trolley with multiple drawers is very helpful for storing lash trays. You can buy various acrylic holders that will store your lashes if you like to work from a tile and also those with separate compartments to store lash brushes etc.