Simone,
Basically, there are three ways to order your tickets:
1) on-line via the International des feux Loto-Québec's official website:
http://www.internationaldesfeuxloto-quebec.com/en/
2) by calling "Réseau Admission" (phone number is available on the website); or
3) in person, at La Ronde's gate. I am sure that there are unsold tickets for most of displays until the last couple of hours.
I suggest to buy tickets in "Silver" level, section 3, 4, 5, or 7. You should avoid sections 1 and 2, plus the first 5-6 rows of sections 3 to 7, because you would not benefit from the inclination of floor; consequently, it could be more difficult to see some water effects (if this kind of effects are included in the display, of course). Please note that it is not possible to choose a specific seat when you purchase your tickets on-line.
Viewing the display from La Ronde is the best. You will benefit from the atmosphere and the proximity between you and the show. Plus, the soundtrack can be well understood throughout the display. Each show begins at 10 pm, but reach your seat before 9:30 pm to enjoy the official ceremony before each display.
These tickets give you the possibility to enjoy most La Ronde's rides and live entertainment.
Keep us informed about your experience!
Frédérick