Few, a few

Few has an almost negative meaning and can be replaced with not many, hardly, or any.
A few has a positive meaning and means a small number of or some.
Note how few and a few are used in the following sentences.

1. You lost marks because you made a few mistakes in your essay.
2. Few people live to be a hundred.
3. We went to Bangalore for a few days.
4. Few people own cars in this city.
5. I have few enemies, but I have a lot of friends.
6. He doesn't speak much. He is a man of few words.

Little, a little

You use little and a little before uncountable nouns.
Little has a negative connotation. It implies a scarcity, and it can be changed to "not much" quite readily. On the other hand, a little has a positive meaning and means "a small quantity of."
The following examples give you a better idea on how little and a little are used.

1. Please wait a little. I am going with you.
2. The old man is seriously ill. There's little hope that he'll recover.
3. He could see little in the dim light.
4. Please give me a little milk to make tea with.
5. He knows a little English. He will be able to talk with you.
6. Little did I know that I would be in for a great surprise.