Getting Tourist Visa to Iran has a simple procedure. Approved Iranian travel agents can apply and get visa for all foreign nationals (except Israeli passport holders)

At present the Iranian Foreign Ministry does not allow American passport holders to travel to Iran independently. Americans are required to travel on escorted tours; either as part of a tour group, or a tailor made individual tour. An exact itinerary, to which you must adhere, is compulsory.

In order to apply and get your visa you must contact to an approved Iranian travel agent . After receiving your personal data , they apply to the Ministry of Foreign Affairs. Your visa will then be authorized by the MFA and faxed to the Iranian Consulate near you . Your travel agent give you a visa authorization number with which you can refer to the consulate to get your visa . The visa authorization number, however, is valid only in the consulate you have asked them your visa to be issued in. The number they give you is just an "authorization". This reference number means that your visa has been authorized and approved by the Ministry of Foreign Affairs but it is not the visa itself.

After your travel agent announce you the visa authorization number you should first get a visa application form from the consulate and follow the requirements of the application form (you may either personally go to the consulate to get the application forms or - if the service available - download it from the web site of the Iranian embassy in your country). Then you should refer to the consulate to lodge your passports and application forms with the visa number they gave you (it can be either a physical presence or by post). Then it might take from one to five days for the consulate to issue your visa.
Normally, all tourist visas issued by Iranian consulates have a "3-month" validity. The visa allows you to stay in Iran for up to 30 days, although the duration of your visa is at the discretion of the Iranian Foreign Ministry.

Visa Section: Iranian Embassy in Ottawa

Types of visa : Entry, Transit, Business, Tourist and Journalist. Fee varies according to nationality of applicant, type of' visa and the existing regulation between countries.
Note: A visa cannot be issued for passports which have a validity of less than 6 months. Exit permits required by all (often included with visa).

Transit visa :
maximum of 10 days. Application to: Embassy or Consulate.
Requirements:
passport, 1 application form, 4 passport - sized photos, special authorization in the form of a reference number issued by the Foreign Ministry in Tehran

Business Visa:
Requirements:
passport, 1 application form, 4 passport - sized photos, special authorization in the form of a reference number issued by the Foreign Ministry in Tehran, business letter.
All the Visa Application forms are in Adobe's Portable Document Format (PDF). To view and print them, you will need to download Adobe Acrobat Reader for your respective operating system.

Get In:

Most overseas travellers will arrive at "Imam Khomeini International Airport" based 37km southwest of Tehran . There are 70 smaller regional airports, for example those in Shiraz, Mashhad, and Isfahan, and these have daily flights to many international destinations.
Dubai has scheduled flights to many Iranian cities, including Tehran, Shiraz, Isfahan, Kerman, Lar, Mashhad, Tabriz, Kish Island, Bandar Abbas, Bushher, Zahedan, and is therefore worth considering travelling to Iran from.
Iran Air connects Tehran with some of the major European cities as well as destinations in Asia and Middle East. European companies landing in Tehran include British Airways, Lufthansa, KLM, Alitalia, Turkish Airlines, Austrian Airlines, Aeroflot and Air France.Here are some of the Middle-Eastern airlines:Saudi Arabian Airlines,Emirates,Syrian Airlines and Egypt Air.So finding a flight to Iran should not be hard.
There are no direct flights from Canada or US at present, but you could travel via either Europe or Dubai.