Saber (to know) means to have information in your mind. Moreover, it means to know about a subject you are familiar with.
Conocer (to know) means to recognize someone or something.
Therefore:
1. I know how to read.
In this case, I would use saber.
In Spanish, this sentence means:
Yo sé como leer.
sé is the conjugation of the verb saber for the first-person singular in the simple present. In this case, I know how to do something, that is, I am familiar with a subject which is the reading.
2. She knows the answer
In this case, I would use saber.
In Spanish, this sentence means:
Ella sabe la respuesta
sabe is the conjugation of the verb saber for the third-person singular in the simple present. In this case, she has information of something.
3. They know María
In this case, I wouldn't use saber, but conocer.
In Spanish, this sentence means:
Ellos conocen a María
conocen is the conjugation of the verb conocer for the third-person plural in the simple present. So, they may recognize María if they look at her.
4. We know Johnny Depp!
In this case, I wouldn't use saber, but conocer.
In Spanish, this sentence means:
¡Nosotros conocemos a Johnny Depp!
conocemos is the conjugation of the verb conocer for the first-person plural in the simple present. So, if we look at Johnny Depp we may recognize him
5. Do you know San Francisco?
In this case, I wouldn't use saber, but conocer.
In Spanish, this sentence means:
¿Conoces San Francisco?
conoces is the conjugation of the verb conocer for the second-person singular in the simple present. So, someone is asking me if I could recognize some place called San Francisco.
6. I know all about birds
In this case, I would use saber
In Spanish, this sentence means:
Yo sé todo sobre aves
As in exercise 1, we use the conjugation sé here. So, I have a lot of information about a subject, that is, birds
