Rail tickets & bus info

1. I will be taking a one-way (tour to Kyoto) from Tokyo. I will be taking the JR rail from Kyoto to Narita Airport - when/where do I purchase my ticket from Kyoto to Narita Airport? Are their any discount tickets? Can I use Credit Card to purchase ticket?
2. I will be staying at Shinagawa Prince Hotel - how do I find info on the bus from Narita Airport to Shinagawa?

It's probably easier to take the Narita Express from Narita to Ueno (tickets for which can be purchased at Narita), which takes ~1hr. From there, the Yamanote line goes straight from Ueno to Shinagawa (and that train line runs in a circle, so if you get on the wrong one, it will take you there either way!) I don't know anybody who has used a bus from Narita.

As for Kyoto to Narita, the shinkansen travels on JR lines and will take you to Ueno. You can take the same Narita Express back to Narita from Ueno then.

Hope that helps!

Oh yeah, whoops. The Narita Express is a train, forgot to mention that. :P

when/where do I purchase my ticket from Kyoto to Narita Airport?

At any JR railway station and at any time within one month before travel date.

Are their any discount tickets?

See here:
http://www.japan-guide.com/e/e2363.html

Can I use Credit Card to purchase ticket?

If you go for a regular ticket, yes. If you go for a Japan Rail Pass, the pass has to be purchased before you leave for Japan.

I will be staying at Shinagawa Prince Hotel - how do I find info on the bus from Narita Airport to Shinagawa?

Here:
http://www.limousinebus.co.jp/en/timetable/narita/shinagawa_...

It's probably easier to take the Narita Express from Narita to Ueno

The Narita Express operates between Narita Airport and Tokyo Station. The Skyliner operates between Narita Airport and Ueno Station:
http://www.japan-guide.com/e/e2027.html

Don't travel via Ueno! Taking the Narita Express directly to Shinagawa will be much more convenient. Likewise, when you return from Kyoto to Narita, change trains at either Shinagawa or Tokyo Station, but not at Ueno.