In general, some is used in positive sentences:
- I got some nice presents for Christmas this year.
- This job is going to take some time.
- Look! There are some large black birds on the roof of the church.
- You have some butter on your chin.
- If you are hungry, there are some biscuits in the cupboard.
- I'm sure I'll return to Japan some day.
- There is somebody on the phone for you.
- I'd like to go somewhere hot this summer.
In general, any is used in negative sentences and questions:
- I didn't get any nice presents for Christmas this year.
- I looked in the cupboard but I couldn't find any biscuits.
- I don't need any help.
- She's so rude. No wonder she doesn't have any friends.
- I don't have anything to wear to the dance.
- I'm not hungry. I don't want anything to eat.
- Do you have any brothers or sisters?
- Did you catch any fish?
- Have you seen any good films recently?
- Does anyone know the answer?
- Are you going anywhere this Christmas?
In fact, the use of some/any is a little more complicated. Following are two common occasions when the above "rules" are "broken":
1. We can use some in questions when offering/requesting:
- Would you like some more tea?
- Could I have some milk, please?
- Do you want something to eat?
2. We use any in positive sentences when we mean it doesn't matter which ..:
- You can come and ask for my help any time.
- Which book shall I read? - Any one. It's up to you.
- You can sit anywhere but here. This is my seat!