Important! The following hints were made mostly for less experienced players. If you had any contact with the first "Advanced Warfighter" game, I guess you won't have to read this section of the guide too thoroughly.
1) First of all, I wouldn't recommend being in a lot of hurry, especially if you had chosen one of the higher difficulty levels. Otherwise you would probably die very soon or you would endanger the lives your teammates. Obviously I wouldn't recommend risking too much, especially since it's very easy to die in this game and you will be dealing with a lot of elite enemy units (including snipers) later during the course of the singleplayer campaign.
2) Try using all available cover areas to your advantage. You will come across a lot of standard or destroyed vehicles. You will also be able to hide behind barrels and brick walls. This will allow you to increase your chances for survival. Additionally, some of the enemy soldiers will have hard time hitting or even spotting you.
3) Make sure that you're using the tactical view all the time, even if you don't plan on using this view to command the rest of the team. The tactical map allows you to see all enemy units and you wouldn't be able to find them on your own. You will also be allowed to use the UAV drone in several missions. This machine can prove to be very useful.
4) Explore your surroundings very carefully. You should try to secure all previously explored zones, so you won't be surprised by enemy soldiers (those who have managed to survive the initial assault). There are many roads leading to some of your target areas. Try choosing less obvious passageways.
5) Most of the enemy soldiers will be standing in the exact same spots each time you load a level, however some of them will be on the move. As a result, don't worry if you can't see them right away. You will have to use the tactical map in order to find their new positions. Also, I wouldn't recommend letting them survive the initial attack, because they would probably try to organize a surprise counter-attack and you could have some serious problems defending against these types of actions.
6) Remember to take good care of your teammates. You won't be punished if they die during the course of a mission, however I'd personally recommend focusing all of your efforts on bringing the entire team to the extraction point. You should be able to take out most of the enemy soldiers on your own, however a friendly sniper may be useful during some of these fights.
7) Make sure that you've chosen a proper team for every mission. Each level will require you to deal with different types of threats. For example, I wouldn't recommend choosing a sniper for a small urban mission, because he wouldn't be able to take out enemy soldiers from larger distances. I guess you won't have any problems figuring out the correct setting of your team. As for the weapons, I'd strongly recommend focusing only on taking single shots. You will also be able to use silenced weapons during some of the missions, however this isn't going to be necessary. Grenades seem to be very useful to take out larger groups of rebel units. You will also be using night vision goggles during two night missions or while trying to explore underground bunkers.
8) Don't forget about the possibility of saving your current progress. This can be done by pressing the K key (by default). The game will create three different quicksave slots, so you won't have to worry about not being able to continue if you've saved the game in a dangerous area. Additionally, each time you succeed with one of the main goals, an auto-save is going to be created. As a result, you won't have to worry too much about having to repeat entire missions, however there are a few spots which will require you to break into enemy territory without being able to save your progress.