Survivor Trophy in Uncharted 3: Drake's Deception

The description here is self explanatory.

It's feasible, depending on what difficulty, you are playing on that this will come naturally, yet even on Easy there is still the chance of timing an environmental error on your part that will result in an accidental death. Be careful once you build up a steady count not to do something reckless and have to start over. The 75 kills can be from melee attacks, gunfire, environmental kills and explosive kills, anything counts towards the total.

Now before going any further, there are 2 Golden Rules you should know before taking on this trophy:

Restarting a Checkpoint to farm kills will not work!

Each time you choose to Restart a Checkpoint, any kills between the last Checkpoint and when you restarted are lost so don't waste your time trying. There is however a workaround but it involves keeping a spare save file. How it works is you kill a bunch of bad guys and pause the action, then either it will auto save or you need to save manually (it doesn't matter which). Now pause and hit 'Load Game' and it will retain the kills you earned allowing you to repeat kills on the same groups of enemies. Where the second save file comes in is if you happen to die and you are not fast enough to pause it to save then load your game, the death will have registered and reset your count. The second save prevents this by having a backup, you will lose a handful of kills should you need to use that back-up but thankfully you won't have to start all over again.

and:

Always leave 1 guy alive

Wipe out most of the enemies you can in relative safety using the method as described above but always remember to leave at least one bad guy alive if you plan to farm the area you are in. If you wipe everybody out, the game forces you to progress via cutscene or by resuming the action but with a change in background music. Once this has passed, auto save will kick in when you pause the game to load the previous area meaning you can not return to where the bad guys were.

With that said, there's a number of locations to do this so just choose whatever suits you but here's a couple of tried and tested locations and methods:

1 - In Chapter 8 you will come to a section which introduces you to the Dragon Sniper rifle for the first time and enemies will spawn in the distance and fire RPGs at you. The rockets are very easy to avoid and you can pick enemies off with the sniper rifle, there are 5 enemies so take out 4 of them then save/load your progress and repeat.

2 - In Chapter 12 you will clear out a large water area with rafts and boats dotted around. Once you clear the place out and ascend the ships mast in the far end of the dock you will get a TAU Sniper and many enemies will spawn in the distance. Pick off 3 them with your sniper handgun and repeat.

3 - In Chapter 19 you will clear out a number of bad guys before coming to an enclosed area which you escape by shooting away the red supporting structure. Once you climb out you will kill a sniper, go to where he was (and picking up his T-Bolt) and you will have a gunfight with several enemies and you'll have a Mag 5 and T-Bolt to wipe out enemies with 1 shot kills. You can kill 7 guys in this area before having to save/reload.

There are a ton of other places so choose wherever you have the most fun and chain the kills together but always leave one lone survivor before saving and reloading. The trophy will unlock when you have killed your 75th enemy in a row without dying.