Spanish question
 

I have not had any spanish classes since spring semester 2001, so I'm a little rusty. :(

Two questions:
When do you use un/una/unos/uno and when do you use el/la/los/las before a noun?

When do you use "ser" and when do you use "estar"?

un, una=a

unos, unas=some

el, la, los, las=the


Use el before singular masculine items (el libro), la before singular feminine items (la pluma), los before plural masculine items (los libros), las before plural feminine items (las plumas).

In a nutshell, estar is used for location, temporary conditions, and the present progressive -and ser is used for the huge majority of everything else.