If you are Canadian, you should know that most Canadians don't need an actual visa sticker in their passports to enter the US in TN status. Such people can present the necessary documents at a US port of entry.
To get an actual visa sticker in your passport, you must apply at a US consulate. This means that you must leave the US, of course. It also means that you need to plan your trip so you have enough time near a US consulate to apply for the visa.
You do not need to wait for your visa to expire. For example, if you are planning to make a long visit to a place with a US consulate before your visa expires and another trip just after it expires, during which you will not be able to apply for a visa, you can apply for the visa during your longer trip.
In your case, it looks like you'll want to apply while you're with your family at Christmas. That could obviously be problematic, since there are likely to be a lot of people in your position, so perhaps more applications at the consulate, and, no doubt, fewer staff. Unless you're planning a long visit, you might want to try to arrange an earlier trip to renew your visa. If you're in the northern US, you might be able to
So, to start the renewal process, you can visit the State Departments page, which in turn directs you to the online DS-160 application form. Don't forget to bring the documents you'll need for the application when you go home. There is more specific information available for those applying in Mexico, which includes detailed information about the necessary documents. I did not find an analogous page on the website of the US diplomatic missions to Canada.
You can find visa appointment wait times on the State Department's website. This may help you in planning your trip. The time for "other nonimmigrant visas" in Mexico currently ranges from one or two days at most consulates to 9 days in Mexico City, while in Canada it ranges from three days in Vancouver to 64 days in Toronto and Montreal.