Summarize:

The Canada Border Services Agency (CBSA) can deny you entry if they have a reason to doubt your ability to support yourself or your dependents while you are in Canada. You can reduce these financial doubts by carrying specific documents with you when crossing the border: Proof of finances (i.e. bank statements); Income tax records (past and present); Evidence of current employment (i.e. pay stubs, an employment ID, notarized letter from your employer); You may be asked to provide evidence that you have responsibilities that will guarantee your return to your home country. Examples of these responsibilities are having a permanent job, home, financial assets or family in your home country. Documents that will serve this purpose are: Proof of current residence, including recent proof of rent payments, copies of your mortgage and utility bills; Proof of your planned departure from Canada (i.e. an airline or other travel ticket that states the time and date you plan to leave); Information about where you plan to go while in Canada, including but not limited to the address, telephone number, and which Canadian citizen you are visiting (if applicable). If you have even one criminal conviction in your past, regardless of how trivial or long ago, you can be turned away by the border officer. Civil traffic violations (such as speeding tickets) and other minor infractions (such as parking violations or littering fines) are exempted. DUI and DWI offenses that may be considered misdemeanors in the Unites States are considered serious offenses in Canada and you can be denied entry for them. If you've been convicted of a felony in the past, you will be prevented entry into Canada unless you've received a pardon, been accepted for rehabilitation and deemed rehabilitated. Individuals with a past criminal conviction are allowed to cross the border as long as conviction has been expunged, but make sure you have paperwork or a letter from an attorney on hand to prove it. This will be determined on-site simply by observing how you look when you cross the border. If you are observed to be in a condition that is likely to endanger public health and safety, or if it will cause you to over-utilize Canada's health or social services, you will be considered inadmissible on health grounds.
Bring enough money for your stay. Bring evidence that you will leave Canada at the end of your visit. Exercise caution if you have been previously convicted of a crime. Be in good health.