Meet nutritional guidelines or eat less?

You can change any of your nutritional guidelines through 'goals' but If you are just starting out and don't know much on what you need I would follow what mfp says. As with any goal, yes the idea is to meet those without going over. Depending on what your caloric goal is some people find it hard to get to or hard to stay under .. if you are under by a little don't worry but try to hit them as much as you can. when you add exercise it will automatically add your exercise calories into your intake calories. Some people find that eating their workout calories helps them, some find it doesn't .. you need to figure out what works well for you. I think most of the goals are pretty accurate, the one I see most about people have issue with is protein because mfp seems to underestimate that and if you go over on that number I wouldn't worry about it. Also sodium is usually a good one to change. Mine sits at 2500 but I changed it to 1500 because I want to lower the amount of salt I eat as I have high blood pressure.

Good luck!