When should I use the following sentences? or what is the difference in the meaning of the following sentences?
Put some lemon in my soup.-this tells how MUCH lemon you want in your soup
Put a lemon in my soup.-you want the ENTIRE lemon (literally, including peel) in your soup.
Put lemon in my soup.-the most basic-you probably want to include the word seasoning, juice or something like that after "lemon" to clarify
Hope this helps!
If you're in a restaurant, you probably want to say, "Could you please add some lemon juice/seasoning to my soup?"