Your missiles particularly air to ground types such as the Maverick tend to behave erratically on many occasions. Try not to fire when you're near any type of terrain obstruction, and when all else fails use the Unlimited Ammo cheat to thwart frustration.
Don't blindly use the default aircraft and Loadout selection for the missions. Watch these carefully, as they do not always make sense. Many times you'll find that the computer gives you the F-14 for a ground-strike mission when the F-18 would be the better choice. Mavericks are awesome at taking out ground targets from a relatively safe distance, so take extras long if you can.
On air to ground attack missions, make sure to fly as low as possible, starting at 20 miles or more from the target. This will make it harder for SAM sites to detect you. When a SAM gets on your tail, wait for it to get a mile or so away and then make an extremely hard turn into its path while releasing flares. Or, when the SAM is farther away, hug the terrain and it will likely hit the ground or a mountain peak instead of your tailpipe.
Have your wingman attack the target first that way he gets most of the enemy's attention and may manage to take out a target or two, making your job easier.
