A great man once said, "Know thyself, know thy enemy."
That was Sun Tzu, the author of The Art of War. We're convinced he knew a thing or two about combat.
We're also reasonably sure he was referring directly to Glu's latest freemium shooter Contract Killer 2 with that above slice of advice, for you'll need to know all about your own capabilities and faculties to really succeed in this game.
But, don't head down to your local library (heaven forbid!) to find a copy of Tzu's war manual to help you with Glu's new iOS and Android shooter. Instead, you should put a brew on, and read through the following guide.
Get to know your environment
Each location you fight in is a set map that you'll play repeatedly, though your starting point on that map is often different.
Because of this, it's a grand idea for you to get to know the problematic areas of a stage's geometry straight off the bat. If there's a spot where enemies always hide, take out the thugs patrolling in and around that area first.
Of course, you can usually get into a fresh position on the map for a better shooting vantage point, so don't stick in a place for too long if you're just not getting the shots in. Wait for the enemy fire to die down, then dash to a new location that exposes your foes.
Movement's really important in Contract Killer 2, generally, and you can get a number of kills in quietly and efficiently just by sneaking up to an adversary and entering the close combat sequence.
If you can remove two or three bad guys without alerting anyone to your presence, you'll make a sizeable dent in any force that opposes you.
It's also a good idea to spend 20 seconds or so before you fire your first shot just looking around the level. If you place an enemy in your sights, he'll be marked with a large red arrow above his head, so when things do get heated, at least you'll have a good understanding of where the enemy fire is coming from.
Get to know your guns
As with 99 per cent of all other shooting games ever, headshots are absolutely the quickest way to bring down your enemy. So, aim for the noggin whenever possible. It's an instant kill if you can hit it.
Since weapon fire isn't completely accurate, you'll sometimes only wound your target when aiming for the head - in these cases, it's advisable to then aim for the body instead of the bonce. Unless you're really close to the target, or have a very accurate weapon at your disposal, you're likely to miss more often than not. So, put a few guaranteed rounds into your enemy's chest to take him out.
The Shotgun - and any other weapon that is more prone to fire in a scattered pattern - is also very effective for headshots. Since the area that shotguns cover with a blast is so large, you're more likely to get a sweet headshot and kill your enemy quickly, especially at short range.
If you want to get shots away quickly when hidden behind cover, by the way, then you need to know one small but important control trick.
Firstly, if you're using a weapon with a scope, don't tap the 'shield' icon to pop your head up before you press the aiming reticle - this adds a fraction of a second onto the shooting process.
Instead, line up the general shot you want to take while hidden behind cover and safe from fire. You can do this by aiming the reticle over your target, and though it won't be completely accurate, it does at least mean you'll be pointing in the general direction when you go to fire.
Next, instead of tapping the 'shield' icon, tap the reticle. You'll pop up and be looking down the barrel of your weapon, likely with the goon you want to off in your sights. The reverse is also true from this position. So, you don't have to stop aiming to take cover - you can just tap the 'shield' on the UI and you'll duck away.
Get to know your gear
Knowing what equipment you'll need to make progress in missions is crucial. If you're on the Airport map and perched high up in a sniping position, then obviously you'll need a sniper rifle (preferably one with a decent sight on it).
However, you might also want to consider taking in an assault rifle - again, with a really good scope attached. The same is true if you're on the ground: you'll be wanting something for combat that's more up close and personal.
Likewise, if it's a Ghost mission - in which you need to get in and out without alerting guards - consider purchasing a few hand-to-hand stealth kill items, for every other weapon is pretty much useless in this instance.
One final tip: should you find yourself in a situation that calls for you to escape quickly - and if you have cash to spare - you should be stocking up on health packs. This will alleviate much of the pressure of the timer counting down, as you can simply keep your head stuck out from cover, blasting away, and use up a medical kit if you start running low on life.
That's your lot. We've given you every little hint and tip we have. Do you have any more you'd like to share? Well, feel free. Just pop a little comment in the box below. Ta.