@jmwismer: As Alec said, the use of "tendría" ("usted") / "tendrías" ("tú") is to be polite.
There are many preferred ways of asking for something, depending on the region and the speaker.
For example, in Mexico we would use the future instead of the conditional:
-
¿*Tendría(s) un bolígrafo? = ¿Tendrá(s) un bolígrafo, por favor? (Even more polite, with "please" added.)
*Never forget opening question marks. We need them to know it's a question.
Other ways to ask for a pen:
- ¿Puede(s) prestarme un bolígrafo? -> Can you lend me a pen?
- ¿Podría(s) prestarme un bolígrafo, por favor? ->
- ¿Tiene(s) un bolígrafo, por favor?
- ¿Me presta(s) un bolígrafo, por favor?
As for the word "pen", there are also plenty of ways to call this object, depending on the region; bolígrafo is a universal word, but local vocabulary preferences include "boli", "lapicera", "pluma"...
In Mexico, we say "pluma", because long ago, the "bolígrafo" was called "pluma atómica", but in most regions "pluma" only refers to a fountain pen, which we call "pluma fuente", to distinguish it from other "plumas".
So don't worry, use the word you've been taught; you'll be understood.