Step 1 - Complete all the stages at the Crushing difficulty
By default, for completing the game, you only receive Legacy Found, but if you want to obtain Progress Demands Sacrifice at the same time, choose Crushing difficulty while starting the game for the first time (you will have to confirm your selection and you will have no problems picking that difficulty level).
While playing the game at Crushing difficulty, keep an eye out for other trophies, i.e. ones connected with collectibles, combat, sneaking, special actions (e.g. climbing to the very top of the tower in Western Ghats, or finding all the tokens and obtaining the Queen's Ruby).
Note - If the Crushing difficulty level proves to be too challenging, you can simply complete the game on a less demanding level to unlock cheats (such as unlimited ammo) that can be used during further playthroughs - using cheats does not prohibit you from gaining the trophy. More info in the section on Progress Demands Sacrifice.
Step 2 - Find all the missing collectibles
You can track your progression in finding collectibles (treasures, photo opportunity locations, optional conversations, lockboxes) on the stage selection screen. Thanks to this, you can easily return to those of the missions, where you have missed collectibles. Unfortunately, each time you do that, you will have to replay the stage from the beginning, and not from a specific checkpoint.
Note -Si Vis Pacem Para Bellum can be included into the group of trophies connected with collectibles. This trophy requires you to use all the weapons in the game, but unlike standard collectibles, many weapons can be found in several locations in the game.
Step 3 - Replay chapters 1-4 without using weapons and explosives
Before you try to obtain minor trophies, it is a good idea to try to obtain The Way of the Warrior. To get this one, you have to replay a large portion of the games beginning without using weapons and explosives. This is not easy, but you should have it easier, since you are already familiar with the stages (especially in the case of the fourth one). Additionally, this trophy does not set any difficulty level requirements and, as a result, you can replay the beginning (including prologue) at the lowest difficulty level (Explorer), where sneaking, or even fistfights do not carry a high probability of dying.
Step 4 - Obtain the remaining trophies
After you have obtained all the trophies mentioned in steps 1-3, there may still be a long way to the platinum trophy, ahead of you. Fortunately, the majority of the remaining trophies are neither difficult, nor time-consuming. In general, these can be divided into two main categories. The first one are connected with additional exploration of stages and these are, among others Yas Queen, which you obtain after finding the Queen's Ruby in Western Ghats, or Marco Po-No for jumping into the water by the dam in Halebidu.
The other category are trophies connected with combat and sneaking. These may be more time-consuming, especially the more demanding ones. For example, you obtain Make an Entrance for killing your enemies with: a car, long weapon, melee, and grenade, within 20 seconds and in this specific order. See the walkthrough for individual trophies in this guide, because it is much easier to obtain those trophies if you try to meet the requirements in specific locations, e.g. where there are groups of enemies that are an easy target.
Pick and obtain trophies from the above two groups one-by-one until you have obtained them all and obtained platinum.