In
Location / Places
Use:
I'm in the park.
She's in the living room watching TV.
We're in the cinema waiting for the film to start.
In London, some of the buildings are very old.
When using 'in' with a place, think of the place from above. If you are within the boundary of the place then you are 'in' it.
Objects
Use:
There's a shoe in the fridge!
My homework is in my bag.
If you want a spoon, it's in the first drawer.
She put everything back in the box.
If one object encloses another object, it is 'in'.
Use:
I'll be there in 10 minutes.
My birthday is in July.
I was born in 1984.
In 2004 I went to Thailand on holiday.
Think of 'in' as non-specific. 'In July' could mean early, middle, or late July but the time is 'in' July. 'In 2004' means sometime in that year. Imagine a calendar, if you say 'in' you draw a border around the time and what you are describing is 'in' that.
Use:
I'm in the car with him.
He's in his seat.
We're in the boat.
I'm in the hot air balloon.
With transport, use 'in' if you bend your knees to take your seat. If you use a large plane you walk 'on' but if you use a small plane you get 'in' by bending your knees.
Use:
He said it in a rude way.
I'm in charge.
Do you have it in blue?
What's in it for me?
I've got him in my team.