Goats are creatures of habit. If you want to maximize the amount of milk you get and make milking easier, you need to develop a regular milking routine, which means using the same place and same procedure every day.
A milking routine requires you to
Have a milking area separate from the other goats (otherwise they will bug you and steal grain from the goat being milked).
Milk the goat from the same side every time.
Wash the udder first, to encourage the udder to let down and to ensure cleanliness.
Milk your goats in the same order each time, unless one gets mastitis. You can choose any order you want, but the goats usually choose the order, with the herd queen going first. If you have CAEV-positive goats, milk them last or use separate equipment.
Other than the rare precocious milker, in order to freshen, a goat first has to have a kid.
Before she produces true milk, a goat produces colostrum. The supply of milk that a goat produces is based on the demand for that milk. If you milk only once a day, you get less milk than you do with two milkings because the goat produces less (unless she has kids still nursing and creating demand). You can milk three times a day and get even more milk, but doing so is generally not cost-effective when you consider the amount of time it takes.
Unless you're bottle-feeding kids, let them nurse whenever they want for the first two weeks. Then put the kids in a separate area each night and milk their dams in the morning before letting them out for the day. The kids keep the dams milked during the day, although you can usually get a little bit from an evening milking. That is, until they learn the routine and rush to their mothers to get that last drop before being locked up.
If you are bottle-feeding and plan to use the doe's milk, you need to start milking right after they kid. You can take their colostrum for feeding the kids or freeze for later use.
To prepare the does for twice-daily milking, put them through the milking routine in the evening whether you milk them or not. That way you can gradually increase their tolerance to grain in anticipation of weaning the kids and milking twice a day. Whether you milk once or twice a day, you need to do it at the same time to ensure that does don't decrease production or get uncomfortable from a too-full udder.