Tourists don't need a visa for Ecuador.
The passport has to be valid at least 6 months counting from the day of your arrival.
At the airport you will get a mark on your passport that confirms your entry into Ecuador, this will be registered countrywide.
Abidance: Maximum 90 days within one calendar year.
Multiple entries are possible in one year if you consider the 90-days-limit.
An extension for more than 90 days costs approximately US$ 250 and must be done before the 90-days-limit expires.
Not adhering to given statement is punished by a fine from US$ 200 to US$ 2.000 and a deportation within 48 hours.