In the video guide below it will explain what are the best classes to rank up in modern warfare 3. What killstreaks are good to have, weapons, riffles, EM's and P90 EM + RF, P90 class and others. Each class is good of course for different maps but you combination that you use it depends on you, this is just a guide of classes to rank up fast in modern warfare 3.
TOC:
Modern Warfare 3 Walkthrough
Modern Warfare 3 Review
Modern Warfare 3 Village Survival Mode Walkthrough
Modern Warfare 3 Enemy Intel Locations
Modern Warfare 3 Wiki
Modern Warfare 3 Achievements
Modern Warfare 3 Trophies