Im making this thread so when people are stuck on a certain part of a level, they can just look here rather than posting. I hope you like it.
1. Choose your destiny
The game offers several levels of difficulty - the higher the level, the harder it is to remain hidden, and the less frequently you'll be allowed to save your game. Skip the easiest level if you want to the game to be any fun at all.
2. Silence is golden.
The ideal way to complete a hit is to do things as silently as possible. Use the silencer on your pistol - you can buy one if you haven't got one, or use your fire wire to keep things quiet. Or perhaps arrange a little accident... because....
3. Pushing is the answer.
You can now push anyone at all just by walking up to them and pulling the right trigger. Which may seem like a lot of fun, but what use is it? Well, it's very useful for pushing people down the stairs, thereby killing them. Killing someone in such a manner results in little noise, and there are also other places they can pushed down or into, such as into crocodile pits and over fences.
4. It was an accident.
And that's not the only way to cause an accident. You can also use explosives to topple chandeliers and the like, crushing anyone beneath. But be careful - you'll have to wait till your target is right underneath, or you'll have wasted your opportunity.
5. Notorious 47
The more noisily you complete a hit, the higher your notoriety will become. And the more notorious you are, the more likely you are to be discovered in the next mission. So try to..
6. Leave No Trace.
Aside from just completing a hit silently, it's also important to get rid of any incriminating evidence. That means hiding or leaving with any extra guns you brought with you, taking your suit with you, and also hiding bodies in skips, crates and so forth. Similarly, make sure you remove the tapes from any video cameras that might have caught you in action.
7. Back from the dead.
Should you be gunned down by enemies, you'll go into slow-mo mode which gives you one last chance to fight back from the brink. Shoot your foes in the head before you die and you'll be given enough health to continue. Although the whole point of the game is not to find yourself in that situation.
8. Guns, guns, guns.
You can purchase a variety of guns with the money you earn during the missions, although again bear in mind this isn't a shoot fest. If you do find yourself having to shoot through a room, grab another character to use as a human shield. Pushing in the right stick to switch to first person mode also helps.
9. Close Combat
47 is now fairly handy with his fists, so if a character does spot you, it's not all over. Punch his face off before he can reach any allies by hitting the right trigger.
10. Mapping it out.
Finally, as in previous games, you have access to a map that shows you the position of all foes, as well as any interesting objects. I personally think this is cheating and hence don't use this, but if you want to go for it.
So that's it, have fun with the game, and don't forget to play it through a few times, trying different tactics, as there's a lot to do in Blood Money, and multiple ways of completing missions.