Here is a rundown of the main conditions:

Permanent Resident Status

Regardless of your age, if you desire to become a Canadian citizen, when you apply for Canadian citizenship you must have:

Permanent Resident status in Canada.
No unfulfilled requirements associated with your PR status.
At the time you apply, your PR status must not be in question. This means you must not be under review for fraud or immigration reasons, have related to your PR status unfulfilled conditions, be under a removal order.

Even if your PR card is expired, you can still apply for citizenship. If you have served in or with the Canadian Armed Forces, you might be able to apply through a fast-track process.

Time Permanent Resident Has Lived in Canada

You must have been physically present in Canada for no less than 1095 days during the 5 years period right before the date you sign your citizenship application. This condition applies to every candidate regardless of age.

You may be able to use some of your time spent in Canada as a temporary resident or a protected person. Each day spent physically under these statuses before becoming a Canadian permanent resident within the last 5 years will count as one-half day, with a maximum of 365 days.

Temporary resident status includes legal authorization to enter or remain in Canada as a temporary resident permit holder, student, visitor or worker.

These requirements don’t apply to children under 18 where a parent or guardian has applied on their behalf for citizenship.

Keeping a record all your trips outside of Canada will help to estimate your physical presence and meet Canada’s immigration requirements. Travel journal may be of a help that you can download here.

Income Tax Filing

Canada immigration requirements also include meeting your personal income tax filing obligations. That’s why regardless of your age, under the Income Tax Act, you must meet your personal income tax filing obligations in 3 tax years that are partially or fully within the 5 years right before citizenship application.

Language Skills

There are two official languages in Canada – English, and French. To receive citizenship, you must prove that you can listen, speak and write in one of these languages. This means that you can:

Take part in short, common conversations on daily topics.
Understand simple directions, questions, and instructions.
Use basic grammar, including simple tenses and structures.
Demonstrate that you know enough general phrases and words to express yourself and answer questions.

If you are 18 to 54 years old, you must add proof that shows your English or French skill level. However, if you are under 18, then you don’t have to meet the language requirement. You must meet the Canadian Language Benchmarks Level 4 (CLB 4) or higher in speaking and listening.

How Well You Know Canada

For becoming a Canadian citizen, you’ll need to take a test of the knowledge requirement. You’ll need to answer questions about Canada’s:

Symbols.
History.
Values.
Institutions.
Responsibilities, rights, and privileges of citizenship (like obeying the law and voting in elections).

The Discover Canada study guide will help to prepare for the tets and can be found here.

Prohibitions

You may not be eligible to become a Canadian citizen for a period if you have committed a crime in or outside Canada. This includes if you:

Are serving a term of imprisonment, on probation or parole in Canada (doesn’t count as the time you have lived in Canada).
Are serving a sentence outside Canada.
Have been convicted in the four years before applying for citizenship of an offense outside Canada or an indictable offense in Canada.

Are charged with, on trial for, or involved in an appeal of an offense outside Canada or the indictable offense in Canada.