What area is your friend going to be in ? Most are pretty automated... Display rooms that are available, push the button or touchscreen and then pay... give the receipt to the person behind the counter they ask how long ( typically 2 hours) , pay and get the key... Alternatively, there are those where you go to the room and there is a machine where you pay... There are some in Ebisu, one in Roppongi, Gotanda, Shibuya... etc. etc.. best to go there with your companion however, as they probably won't let you enter alone... I'm sure others here can give maybe more detailed information, but you need to advise where and budget of your friend