Making Requests

You must love the internet. There are so many resources out there to take advantage of, it's just silly.

Today, I was thinking about making requests, and I found a little write up on Google Answers (credits to the folks who asked and answered - original link). I found this section most valuable, although it gets into a lot of theory. I put in bold the text most utterly valuable.

First, a clarification about the use of "podría". Podría is the verb
"poder", translatable as "can" / "could", "may", "be able", depending
on the context. The desinence "ía" is what gives its conditional
conjugation. But you wouldn't necessarily use this verb to ask
something in the conditional mode:

"¿Podría darme una servilleta?" corresponds exactly to:

"Could I have a napkin?" or "May I have a napkin?" or more literally
"Could you give me a napkin?"

But there is still to consider the equivalent to:

"Would you give me a napkin?" which is:

"¿Me daría una servilleta?" where the conditional form is given by the
desinence "ía" added to the verb "dar" = "to give"

One major difference between English and Spanish is that the latter is
strongly desinencial, so it doesn't need auxiliary verbs to construct
tenses, as English does (in this case, "would"). Now, this conditional
form, ommiting the verb "poder" ("podría", or "podrías" in a
colloquial context) is by large the preferred usage. Still, the form
preceded by the verb poder is not uncommon, as a way to emphasize
politeness.

Also, you can chose to ommit the conditional conjugation:

"¿Me da una servilleta?" The approximate English correspondance would
be: "Do you give me a napkin?", which would not be used in that
situation. Now, in Spanish, this option is at least as much used as
the conditional one, if not more. This one sounds closer to the
imperative form, but it's not it (what would be "Deme una
servilleta").

A slight and curious difference between the usage of the conditional
and non-conditional form for making a request:

"¿Me da una servilleta, por favor?" and "¿Me daría una servilleta?"
sound similarly polite. If you ommit "por favor" (please) in the first
case, you risk to sound a bit impolite (obviously, depending on your
general attitude and tone).

So, we can configure here an increasing scale of politenes:

1. Deme una servilleta. (imperative: mostly rude)
2. Deme una servilleta, por favor = ¿Me da una servilleta? (not
particularly kind, but OK, in the limit depending on you tone)
3. ¿Me da una servilleta, por favor? = ¿Me daría una servilleta?
(polite enough, most used)
4. ¿Me daría una servilleta, por favor? = ¿Podría darme una
servilleta? (particularly polite)
5. ¿Me podría dar una servilleta, por favor? (most polite)

Please take in account that not always the more polite the better,
specially in very colloquial situations where the excess of politeness
would sound affectionate or snob. To walk in the safe side, always use
options 3 or 4 and you'll do OK.