Ask if an item exists in a store.

Hay - "is/are there," this is probably the most common way to ask for something in a store (e.g. ¿Hay manzanas? Are there any apples? Or, do you have apples?).
Tener - this verb is most often used in the third person plural form (¿Tienen carne molida? Do you have ground beef?).
¿Dónde está(n) el/la (los/las) _______? - This is a more familiar phrase which assumes the store stocks what you are looking for and which means, "where is/are the____?." (¿Dónde están las uvas? Where are the grapes?)

One important difference between English and Spanish is that questions using the simple present tense in Spanish do not require an auxiliary verb. Most verbs in English use the auxiliary verb "to do" to make a question (e.g. Do you have milk?). This is not necessary in Spanish (e.g. "¿Tienen leche?").

Another important point is that you will often find that you don't know the exact term of a certain item that you are looking for. There are some expressions that will help you explain what you want.

No sé cómo decirlo en español, pero estoy buscando algo para + infinitivo.
I don't know how to say it in Spanish, but I am looking for something for + gerund.

Estoy buscando algo para golpear clavos. (un martillo)
I am looking for something for hitting nails. (a hammer)

No sé cómo se llama en español, pero quiero algo para + infinitivo.
I don't know what it's called in Spanish, but I want something to + infinitive.

Quiero algo para lavar un carro. (¿Jabón? ¿Una esponja?)
I want something to wash a car. (Soap? A sponge?)

announcement / advertisement - anuncio (m)
cheap - barato (m)
to look for - buscar (m)
expensive - caro (m)
catalog - catálogo (m)
shopping center - centro commercial (m)
mall - almacen (m)
to find - encontrar
tag - etiqueta (f)
publicity - publicidad (f)
store - tienda (f)