There is one thing missing from the other answers:

In every hotel I ever stayed in (in total about 50), they tell you in person what the check out time is while you check in. They tell you even if you don't ask. If you book through a website or a travel agency doesn't matter, the one telling you about checkout times is the person who checks you in at the hotel. If they tell you something and you don't understand what they mean, ask them what they mean, because it might be important.

In cheaper hotels you can usually check out up to 1 hour later than the checkout time without any problems, but the more expensive the hotel the more likely there will be an extra charge.

If you realize that the stated checkout time won't work for you, you need to let the hotel know in advance. They will always be able to find a reasonable solution, be it a late checkout, storing your luggage for you, or something else - they might even allow you to keep the room at no charge, as long as you're gone the next morning. But the prerequisite is that you tell them first. By occupying a room without booking it, you are the worst kind of guest they could wish for, and they have no reason to be nice to you.

There is one thing missing from the other answers:

In every hotel I ever stayed in (in total about 50), they tell you in person what the check out time is while you check in. They tell you even if you don't ask. If you book through a website or a travel agency doesn't matter, the one telling you about checkout times is the person who checks you in at the hotel. If they tell you something and you don't understand what they mean, ask them what they mean, because it might be important.

In cheaper hotels you can usually check out up to 1 hour later than the checkout time without any problems, but the more expensive the hotel the more likely there will be an extra charge.

If you realize that the stated checkout time won't work for you, you need to let the hotel know in advance. They will always be able to find a reasonable solution, be it a late checkout, storing your luggage for you, or something else - they might even allow you to keep the room at no charge, as long as you're gone the next morning. But the prerequisite is that you tell them first. By occupying a room without booking it, you are one of the bad guests, and they have no reason to be nice to you.