Paris to Nice: Do I need to pick up TGV tickets from station or print from home?

Do choose France, and then on another screen, do choose print at home. This works best if you can pick the nonrefundable Prems fare. US credit cards can be problematic, but Canadian credit cards may be better, or PayPal works great for the Prems fare. See also notes at http://www.ricksteves.com/travel-tips/transportation/trains/france-rail-passes#ticket-tips.

The old and reliable trick is to pick Antarctica for your ticket pick-up. On the Paris-Nice route you can then print out your tickets at home. The train attendant will scan the ticket electronically, probably not until you are in your reserved seat.

I recently purchased tickets to travel from Nice to Paris via the iDTGV and the website would not let me use PayPal. I chose France as my country and was easily able to print the tickets at home.

Yes, choose "France" as you ticket collection country, then choose "print at home." You'll get an e-mail with an attached PDF. You can print as many copies as you like (I'm the "nervous" type and put copies in each suitcase). It will say you need A4 paper, but 8.5 x 11 works fine.

You don't need to show anything before boarding the train. On the train, the conductor will need your printout and your passport. Just give him/her both of these, and you're set.

Last year I purchased tickets online and for a few of them I did not have a print-at-home option. I chose France as the pickup country and was able to collect all the tickets (that I could not print at home) at the first train station, from one of the ticket agents rather than from a machine. You will need the credit card you used to purchase the tickets in order to retrieve them (doesn't matter if the credit card has expired in the meantime, take the original card).