You can find the values for common food items online or there are many nutritional resource texts books that can give you this information. A few very helpful sites that I have found to give you complete nutrition information are following:
If you consume fast food or restaurant food items, the websites will have nutritional information - for example: www.panera.com has a full and complete list of every food item on the menu.
One other suggestion I would make is to measure your food. This is usually a real eye opener when people start to measure what an actual serving of food looks like. One serving of pasta is ½ cup ~ most of us get about 3 times that on our first serving. Understanding what you are eating and serving sizes is why moderation is so important. When people want to lose weight they automatically take things away from the diet. You don't have to deprive yourself of things you want to lose weight. You must however; control what you are consuming but adhering to portion and/or serving sizes. I challenge you to use the tools I have provided to you above for at least 2 weeks and see if you notice a difference.
The second part of this question: How do I determine the right amount of calories? There are a couple of answers to this question. Most approximations are done through formulas using height, weight, age and activity level. This formula is called the "Harris Benedict Equation" and it. Although this equation can seem quite cumbersome it is definitely worth understanding. You can also go out to www.myfoodpyramid.gov to get a caloric estimation as well as a sample meal pattern.
Other methods of determining caloric needs include:
RMR - resting metabolic rate (measures gas exchange - give the most accurate data)
The "quick" method (based on total body weight) - does not take into account activity levels or body composition
Understanding your calories needs and making a plan to get to the calories you need on a daily basis to gain weight, lose weight or maintain weight is the first step to gaining a healthy lifestyle!