Useful vocabulary for speaking English.

You may wish to speak fuent English. In this case, you'll have to know some conversational cliches.  They will certainly help you to deal with daily problems such as buying grocery, asking for direction, offering help, introducing people.

1. May I help you? 2. What can I do for you? 3. Is there something I can help you with? How much is this?

Yes, I'd like to buy these razors. I'm looking for the cameras. No, I'm just browsing. Thanks anyway.

Okay, that'll be $6.85 with tax. They're in Aisle Two. Ok. It's $4.95.

Such conversational phrases you will find here - elementary level  and here - high intermediate level. 

You can increase your vocabulary by learning topical vocabulary, i.e. words divided into categories by different topics such as Food and eating, School and studying, Shopping.
You can find some topical vocabulary here. 

More topical vocabulary. 
Family.
Jobs.    Jobs1.  Jobs2.
The city.   Buildings in the city.   Downtown. 
House. Rooms in the house. Places to live in.  Things in a house.
Giving directions. 
Shopping. 
Clothes.  Clothes1. Shoes.

Food.    Fruit.   Vegetables.  Vegetables1. Breads. Desserts. Drinks.
Restaurants. Restaurants1. Restaurants2.
Kitchen.  Kitchen knives.  Dishes and plates.

Holidays, parties.  Holidays1. Party names.
Halloween. 
Christmas.  Food at Christmas.
Thanksgiving.
Valentine's Day.

Travel. Airport.  Hotel.

Typical day. 
Character and people.
School.  School subjects. People at school.  Tests. 
Weather.   Weather1.

Crime verbs. Types of crimes. Criminals.
Court and Justice.

Health and illness.   Injuries.  Aches and pains.

Animals.  Animals1.  Farm animals.   Cat breeds.  Dog breeds.
Car.  Car parts. "Car" verbs.
Flowers. 
Reading.    Reading1.  Parts of a book.  Types of books. Newspapers. 
Sports.   Sports1.

You can find more topical vocabulary and exercises to do on this site.