I like traveling abroad without deciding much. Maybe only air ticket and visa.
But if you want to get a good deal such as accommodation, it might not be a good idea. It is better to check website constantly. Surely not everyone is good at planning. Do not worry.
The most significant things are two: Objective and Budget. Let me mention more about these things.
When you want to travel abroad, you want something away from a daily life: Scenery, Foods, Culture (Anime), Tradition, Art or maybe Shopping. Otherwise, Feelings, Ideas or any other thing. That is, you expect something that you never experienced before including the pursuit of something different or better than daily life.
Then you need to prioritize these objectives. Some of people don’t know what they want or why they travel there. If your objective is clear, your journey would be more meaningful.
Budget / Class Range
If you are too fortunate/lucky, no need to think about money. However, many people have budget limit. You need to decide where to invest such as accommodation, foods, experience, shopping and etc. In Tokyo, price range is very wide, I would say. You can experience something luxuriously. Or you can limit your spending. You can find Japanese Fast food with the minimum of 4 USD in Tokyo. In terms of accommodation, you can stay with the minimum of 15 USD. Of course, it depends on the type of accommodation and season though.
I can tell you a bit about culture side related to your objective from my perspective in person.