Pay attention to the job classes you choose. You’ll often have to split up your team, and you’ll want to make sure support classes are tagging along with classes that can handle direct combat.
Similarly, make sure you’re matching the appropriate gear with each unit. Put the big guns in the hands of those who can use them best, and the support equipment with those who can afford to take a turn off of shooting.
In the Escape Plan levels, take things slowly and consider each move carefully. You’re at a disadvantage from the start in these missions, so you can’t afford to act like a commando.
By contrast, the Bomb Defusal plans demand a little bit more recklessness. You’re on a timer, so to speak, with each turn costing you five seconds. Put your strongest units out there to catch the attention of the enemy while other units get to the bombs.
When leveling up, spend your stat points wisely. Each class has its role to play, and there’s little point spending valuable stat gains on things a unit won’t need.
If a particular mission is giving you trouble and you can’t seem to strategize your way around it, head back to an earlier mission to grind up some experience or cash for new gear. It can sometimes make a big difference, and if nothing else it will give you more practice.
Examine each area carefully before you enter. Think about places where terrorists could be hiding, and make sure someone is covering that area. Don’t forget to keep an eye on doors and other entrances.