You should never have smoke when using your oven, unless you're using the broiler; and then the smoke is minimal.
The first thing that comes to mind is something has spilled in the oven and is now burning off. So be sure the oven is clean.
Do you have an electric oven? The next thought is that you may be placing the food to close to the top eletrical unit.
Another thought, are you cooking the meats at the correct temperature? Most meats are cooked at 375 or less. Some receipes may have you start at a higher temp and then lower it.
Are you using the correct size baking dish to prevent juices from overflowing?
Does this only occur with meats or other foods also? If all foods than you may want to have a repair man take a look at the oven.