Canadian credit cards work almost universally in the US. You will be charged the amount of US currency after it gets converted to Canadian dollars at the bank rate plus a foreign transaction fee. This is now commonly 2.5% for the majority of current credit cards issued by Canadian banks. Whether this amounts to much depends on what you intend spending on.
The majority of US ATMs work with Canadian debit cards, which will give you US funds at the bank rate plus a conversion fee and a foreign withdrawal fee which can be $5 or more, so if you go that route, try to make the least amount of withdrawals.
Canadian debit cards do not work for US debit transactions, so when asked somewhere if you will be using debit, the answer will be no.
Some banks recommend that you call them to inform them of upcoming travel, but this is less necessary than it used to be. Your bank may have an interface to set your travel dates and destination online or you can do it by phone. It is not necessary, but can reduce the chance of having a transaction blocked. If you do not see a policy about this from your bank, give them a call.
A number of Canadian banks offer pre-paid foreign cash cards. You can get one which will work to lock in the rate and avoid fees. You can also get US cash from Canadian banks, and it is a good idea to do so. Tipping is expected in the US even more than in Canada, so it is advisable to ask for small bills when you get US cash. Some tolls still only accept cash, so definitely take some if you are driving, either in Canada, or at a currency exchange, or US banks when you enter the US.