1. We use no article for most companies

Microsoft and Google dominate the online search business.
I work for HSBC in Hong Kong.

2. We use no article with Years, months, days

In 2001, on Thursday

3. We use no article with special times of the year

At Christmas, at Easter

4. We use no article with some parts of the day

At night, at midnight
(but ‘in the morning’, ‘in the afternoon’)

5. We use no article for languages.

I can speak English and French.

6. We use no article with means of transport (in general)

By car / taxi / train / bus / coach / plane, on foot
(but ‘the train to Barcelona’)

7. We use no articles with meals (in general)

Breakfast / lunch / dinner
(but ‘the dinner we had last night’)

8. Note the use of ‘preposition + no article’ with certain places, when the purpose of the place is more important than the actual place itself.

a. In / to

hospital / prison / bed / class / court

I spent two days in hospital.
I went to hospital for a check-up.

b. At / to

Work / school / university

I was at work yesterday until 8 pm.
Usually I go to work by bus.

c. Note how we use ‘home’

I was at home yesterday evening
What time did you go home?