1. Don't rush. Acting too fast is a definitely bad idea in Hitman. You should start with a very thorough scouting of each new map. Don't worry if in case of such giant maps like Paris it takes few hours. Well knowledge of the contract's area of operation will be profitable in the future as it will allow you to move through the map more freely and quickly reach the assassination locations. While uncovering the map, notice such things like unique assassinations locations, position of quest items and disguises, weakly protected entrances.
2. Avoid detection at all costs. Well knowledge of the map, using disguises adequate for the location, moving in crouching position, careful observation of your surroundings and using additional items (like coins) that allow distracting enemies can help you in remaining hidden. If you are detected, consider loading the last game save. Situations when you are detected by single, unarmed people are exceptions. In that case you can try escaping and changing disguise - you won't fail the mission, but you will receive a score penalty at the end. Don't participate in shootouts with armed guards as it won't help you in achieving the goals. Instead, the quick arrival of reinforcements will make Agent 47's situation much worse.
3. Use disguises that are effective in the currently explored location. In Hitman each disguise is unique in some way. For example, the common worker disguise that is easy to obtain can provide you with strongly limited access to heavily guarded places while VIP clothes that are hard to obtain can allow you to travel freely through almost the whole map. Try to learn the pros and cons of each disguise (they were described in our walkthrough). Don't be afraid to frequently change your clothes depending on what you currently need - clothes that aren't used at the moment won't disappear from the map and you will be able to return for them later in the mission.
4. Don't leave any trail behind you. Most of all you should always hide the bodies of stunned or killed people. It is best to hide bodies in closets, chests and other large containers. If it isn't possible then at least hide them in brushes or other places that aren't checked by anyone. You should also check if the people you eliminate don't drop some items like for example weapons. Such items might cause other nearby people to become suspicious.
5. Select difficulty level adequate to your preferences. In Hitman you cannot select difficulty level in classic way (easy, medium, hard etc). Mission difficulty depends on whether you want to use additional "handicaps" during the game. If you don't feel strong enough, you can regularly help yourself with the instinct (it will for example allow you to identify main mission targets), markings that inform you about enemies that can recognize Agent 47 (dots above their heads) and markings that lead to places related to occasions for eliminating targets in unique ways. Deactivating all these hints will greatly increase the amount of time needed for exploring the map and it will make it much harder to remain hidden.
6. Don't try completing everything at once. New Hitman encourages the players very STRONGLY to repeat missions many times in order to gain more experience points and reach higher ranks. So don't worry if during your first attempt you will miss something or won't fully understand a specific situation. When repeating mission, use the previously obtained knowledge and keep checking whether the game haven't unlocked new starting locations (for example a starting point in a kitchen in crew disguise) or stashes with supplies sent by Agency (for example sniper weapon or explosives).
7. Save the game frequently. In Hitman frequently you must be very precise when it comes to avoiding threats and eliminating targets. It is very easy to make a mistake that will for example alarm all enemies or startle the attack target. Due to that, you should frequently save your progress. The game uses auto saves, but you shouldn't depend only on this feature. Despite their presence, after a mistake you might be forced to repeat last few dozens of minutes of the game.
8. Playing offline or online? In the new Hitman game you can decide whether you want to play it offline or online. Playing online is a definitely better idea since it allows you to complete challenges (they give you experience and allow unlocking new mastery levels in specific missions) and to use other "social" features of the game (rankings of best players, new contracts etc). Sadly, online mode also requires a constant connection to internet. Whenever you lose connection, you will be moved back to the main menu without the possibility to save your progress (that is one of the reasons why in the previous point it was recommended to save the game frequently). What's important, both modes are independent from each other. It means that if you start a mission in online mode, you will have to complete it in online mode. If in the meantime you lose internet access, you won't be able to complete it until you regain connection - the only alternative will be to start that mission from start in offline mode.