I work in a games studio making console and mobile games with mid to large budgets in a range of genres. I work on the console games as part of the game design team. I specialise on the content side of the games- working with artists, level designers, audio and writers.
A normal working day is from 10am to 6pm. Sometimes there are reasons to come in at different times for meetings.. especially if I am working with people in other timezones.
There is a lot of travel involved in my job too- as working in games more often than not requires co-operation with other teams around the world. It is unlikely everyone involved in making a modern game will be in the same studio.
My tasks massively vary from day to day, and that is probably the best part of the job. But most of the average day will be spent communicating design and discussing creative solutions- whether in meetings or just at people's desks.
Doing creative work is hugely energising, and if you can enthuse others about what you are doing then it can also be extremely rewarding. Seeing concepts you have been a part of come to life is what its all about.
You can't always expect to be working to a direction that you will personally appreciate. If you hate cats with a passion and it is decided that the game will revolve around cats- then you have to dig deep, find that motivation and start researching your mortal furry enemy.
The technology requirements for a game designer are quite low. But experimenting with making a small game at home through something like Unity will give you the grasp in all areas- art, scripting, animation, UI, audio- that will give you that level of knowledge to discuss with each of these other disciplines in a design capacity. And it will also develop the skills required for creative problem solving.
I would say just how much design is actually required on a game.