If you are a Canadian citizen:
1. You can find yourself a job, then apply TN visa at the border crossing, this requires annual renewal.
2. If you want to move and immigrate to the US. Then you need to have H1 visa.
3. For Canadian corporation transfer employee to its subsidsiry, you need to have L1 Visa. Company would do all this for you.
If you are visiting in the US, you are only allow to stay in the US, no more than 183 days in a years.