The easiest way to do this is to use a web service like cron-o-meter or fitday to track what you eat. Typically you enter foods from a drop down menu or by searching a database (easier than it sounds). You might have to choose between different types of salmon, or different levels of fat trim on beef cuts. The program then pulls information on fat/protein/carb percentages and other nutrients from the usda database and does all the calculations for you.
Some food diaries to look at:
You can also easily search information on different foods at http://nutritiondata.self.com/ from the search at upper right. And they have a handy tool to look for foods that are high or low in certain nutrients.