Network Settings can be the most important settings that affect your hit registration in CS:GO, especially if you already have your computer set up correctly. So, we will go into this first.

There will be two parts to optimizing your network settings: Network Adapter (hardware) settings and your Windows (software) settings. It is very important you do both of these for best results.

Hardware
Open your Advanced network adapter settings:
Open Device Manger
Network Adapters
Right click your current network adapter
Properties
Advanced tab
Apply the following values as closely as possible:

Originally posted by author:

PROPERTY VALUE
Adaptive Inter-Frame Spacing Disabled
Flow Control Disabled
Gigabit Master Slave Mode Auto Detect
Interrupt Moderation Disabled
Interrupt Moderation Rate Off
IPv4 Checksum Offload Disabled
Jumbo Packet Disabled
Large Send Offload V2 (IPv4) Disabled
Large Send Offload V2 (IPv6) Disabled
Locally Administered Address Not Present
Log Link State Event Enabled
Maximum Number of RSS Queues 2 (Maximum)
Packet Priority & VLAN Disabled
Receive Buffers (Maximum)
Receive Side Scaling Enabled
Speed & Duplex Auto Detect
TCP Checksum Offload (IPv4) Disabled
TCP Checksum Offload (IPv6) Disabled
Transmit Buffers (Maximum)
UDP Checksum Offload (IPv4) Disabled
UDP Checksum Offload (IPv6) Disabled
Wait for Link Enabled
Green Ethernet Disabled

Press OK
Reboot your PC for these changes to take effect.

Open a Command Prompt as Administrator.
Press Start button
Type "cmd" without quotes
Right click on Command Prompt
Click Run as Administrator

Enter the following line into Command Prompt as Administrator, and press Enter:

netsh int ip set global taskoffload=disabled

Example:
Reboot your PC for these changes to take effect.

HPET (High Precision Event Timer) settings in Windows can cause major issues if configured improperly. The default settings are acceptable, but not optimal. Here you will find the most optimal settings that have been tested and confirmed by many people, including myself and FREETHY. Configuring the Timer Resolution is also important to reduce system latency, as Windows does not optimize this by default.

You will be performing 3 actions to change your HPET settings. Disabling HPET, disabling synthetic timers, and disabling dynamic tick which is a power savings feature for laptops.

Open a Command Prompt as Administrator.
Press Start button
Type CMD
Right click on Command Prompt
Click Run as Administrator

Enter the following lines into Command Prompt as Administrator, one at a time, and press Enter after each line:

bcdedit /deletevalue useplatformclock
bcdedit /set useplatformtick yes
bcdedit /set disabledynamictick yes

To check if you've completed this correctly, enter the following line and press Enter:

You should see these 2 lines at the bottom of the list:
Reboot your PC for these changes to take effect.

In order to change the default Timer Resolution, you will be using a program called Intelligent Standby List Cleaner or ISLC. This is a free program by Wagnard you can download from this link: web [www.wagnardsoft.com]

Open the program and it will show your Current timer resolution, which will usually be 1ms. You want to change this to 0.5 at all times, so here is how.
Check the box by Enable Custom Timer Resolution
Type 0.5 in the box by Wanted timer resolution
Change ISLC Polling Rate (ms) to 500
Click the Start button
Minimize the program to the system tray
You're done. This is how it should appear before you minimize:
Now your HPET settings and Timer Resolution are set and games may feel slightly more responsive.

Changing some Nvidia Control Panel settings can help reduce latency in your games, if you have an Nvidia graphics card.
Right click anywhere on your desktop
Click NVIDIA Control Panel
Click Manage 3D settings on the left column
Here is the recommended configuration. The most important settings are highlighted.

FEATURE SETTING
Image Sharpening Sharpening off, Scaling Disabled
Ambient Occlusion Off
Anisotropic filtering Application-controlled
Antialiasing - FXAA Off (optional)
Antialiasing - Gamma correction On
Antialiasing - Mode Application-controlled
Antialiasing - Setting Application-controlled
Antialiasing - Transparency Off
CUDA - GPUs All
DSR - Factors Off
DSR - Smoothness Off
Low Latency Mode Ultra
Max Frame Rate Off
Multi-Frame Sampled AA (MFAA) Off
OpenGL rendering GPU Auto-select
Power management mode Prefer maximum performance
Preferred refresh rate Highest available
Shader Cache On
Texture filtering - Anisotropic sample optimization On
Texture filtering - Negative LOD bias Allow
Texture filtering - Quality High performance
Texture filtering - Trilinear optimization On
Threaded optimization Auto
Triple buffering Off
Virtual reality pre-rendered frames 1
Virtual Reality - Variable Rate Super Sampling Off

Click Apply

Here are some tweaks you can implement in the Windows Registry that can improve network performance, therefore reducing latency in games.
Press Windows Key + R
The Run dialog box should appear
In the box type regedit and press Enter or click OK
In the left pane of the Registry Editor window, navigate to the following locations in the registry. Using the arrow-keys on the keyboard makes this much easier to navigate.

Windows implements a network throttling mechanism. The idea behind this throttling is that processing of network packets can be a resource-intensive task. It is beneficial to turn off such throttling in order to achieve maximum throughput.

Navigate to:

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile]

Right click anywhere in the right pane of the Registry Editor
Click New > DWORD(32-bit) Value
Name this new value NetworkThrottlingIndex and press Enter
Double click the new DWORD and an Edit box should appear
Type ffffffff into the box for Value data
Select the Hexadecimal radio button
Press OK

Multimedia streaming and some games that use the “Multimedia Class Scheduler” service (MMCSS) can only utilize up to 80% of the CPU. The “Multimedia Class Scheduler” service (MMCSS) ensures prioritized access to CPU resources, without denying CPU resources to lower-priority background applications. To modify this for pure gaming or streaming, apply this tweak.

Navigate to:

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile][/quote[
Right click anywhere in the right pane of the Registry Editor
Click New > DWORD (32-bit) Value
Name this new value SystemResponsiveness and press Enter
Double click the new DWORD and an Edit box should appear
Type 00000000 into the box for Value data
Select the Hexadecimal radio button
Press OK
You can change the priority of games in the same registry hive.

Navigate to:

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games]

Change the following values:
Double-click GPU Priority
Type 8 into the Value data box for gaming
Double-click Priority
Type 6 into the Value data box for gaming
Press OK

Done! Reboot your PC for these changes to take effect.

Enabling MSI mode for your GPU can decrease your system latency. MSI in this context stands for Message Signaled Interrupts, which has nothing to do with the motherboard company Micro-Star International Co. Ltd., also known as MSI.

A brief excerpt from Wikipedia:

MSI increases the number of interrupts that are possible. While conventional PCI was limited to four interrupts per card (and, because they were shared among all cards, most are using only one), message signalled interrupts allow dozens of interrupts per card, when that is useful.
source [en.wikipedia.org]

To enable MSI mode for your GPU you will be using MSI mode utility v3. This program is free, and can be downloaded from the following link:

web [forums.guru3d.com]

EXERCISE EXTREME CAUTION. THIS TWEAK CAN CAUSE BLUE SCREENS AND SYSTEM CRASHES IF DONE IMPROPERLY OR IF NOT SUPPORTED BY YOUR SYSTEM. IF YOU ARE NOT SURE WHAT YOU'RE DOING LEAVE IT ALONE.
Open MSI mode utility v3
Look for your NVIDIA GPU on the left column
Under "supported modes", look to see if it reads "Msi"
If it shows Msi is a supported mode, check the box under the MSI column
Change "interrupt priority" to High
Press Apply at the top-right of the window
Reboot your PC for this change to take effect.

More information about MSI mode is available on the aforementioned forum post, and from a quick Google search.

Special thanks to Hertz0g and Drax for recommending this tweak.

You want your game to be able to send/receive as much data as possible so you get the smoothest and most instant response. This is a commonly known tweak but some people forget to do this. Note: you need a good connection for this to work properly.

Settings > Game > Max Acceptable Game Traffic Bandwidth > UNRESTRICTED

Alternatively, you can change your rate setting manually:
Launch CS:GO
Open console (~)
Type rate 786432
Press Enter
The most effective method is to add rate 786432 to your autoexec.cfg so it never gets changed when the game receives an update or upon reinstallation. If you are unfamiliar with autoexec files, please refer to the Prosettings guide in the link below:

prosettings [prosettings.net]

There is a sound tweak that can be used to greatly enhance your ability to hear footsteps and sounds from a distance. Hearing things from further away can help you have an advantage or upper hand over your opponents. Note: This tweak will not be available to everyone. It depends on your particular audio setup. You simply have to check and see if it's available.

On your Windows 10 taskbar:
Press Start button
Type sound output device properties
Click on Sound Output Device Properties when it appears in the search
Make sure Spatial Sound is turned off
Scroll down to Related Settings
Click Additional device properties
Navigate to the Enhancements tab
Check the box beside Loudness Equalization if the option is available

This tweak effectively compresses sounds in CS:GO (and anything else you do on your PC). This makes quiet sounds the same volume as loud sounds. There is a noticeable difference in the audio.

This can be disorienting at first, until you adapt to it, therefore some people may not prefer it. Distant, faint sounds will sound very close to you, but at least you can hear them. You can always go back if you don't like how it sounds. For me, I strongly prefer this setting because I want to hear everything clearly.