I don't use dual boot but for many its something which is very attractive, personally I don't care much for Microsoft, as nowadays pretty much anything can be accomplished in Linux. So while I'm strictly in the single boot brigade, dual booting is still popular.
However you're here because you want both...after all what-else would a super nerd want ?
Making this happen included a certain obstacle known as UEFI with secureboot. Alot of people are having trouble installing Ubuntu 14.04 alongside Windows 8/8.1 on systems with the UEFI firmware (Basically all new devices) or post 2011.
Create a Live USB of Ubuntu 14.04
Universal USB Installer is suggested if you are doing this from Windows and UNetbootin if from Linux (use this guide here). Or I highly recommend Linux Live which is available here especially if you are coming from Windows 8/8.1
Make sure the USB stick is formatted fat32.
Make room for Linux OS
To create a partition in Windows 8/8.1 Open Control Panel and enter 'disk' in the search box (top right) then select "Create and format hard disk partitions" (right below Administrative Tools)
Now from the Disk Management Tool, right click on the drive you want to partition (Most likely the C drive) select 'shrink volume'
[Make sure you understand how your particular HDD is partitioned before messing around] After you create the free space, leave it as is for now.
Disabling 'Fast Startup' is recommended
Go to:
Control Panel > Hardware and Sound > Power Options > System Settings > Power Button options *uncheck 'Turn on fast startup box'
Disable secureboot [Mandatory]
Secureboot only allows bootloaders that are signed in to the UEFI firmware.
How to disable secureboot
Move cursor all the way to the right of the screen so the settings menu pops out.
Select 'change PC settings'
Now things are a little different between Windows 8 and 8.1 from this point.
For Windows 8:
Select 'general' under PC settings and then 'advanced startup'
then 'restart now'
For Windows 8.1:
select 'update and recovery'
then 'recovery'
then click 'restart now' under advanced startup
*this wont restart system right away. what it does is next time you boot, an options menu will appear.
How to access the UEFI settings
Restart
A blue screen should appear 'Choose an option'
select 'Troubleshoot'
In the 'Troubleshoot' menu, select 'Advanced Options'
In 'Advanced Options menu' select 'UEFI Firmware settings'
In the 'UEFI Firmware settings" select 'restart' which will reboot
system into UEFI settings
Once system reboots into UEFI utility
Use the arrow keys to navigate to [Boot]
Then navigate to [Secure Boot] Press ENTER to select it
Use +/- keys to change between enable/disable
Change to 'Disabled'
Confirm when prompted
Press F10 to save changes and exit
Next Windows will boot normally (secure boot disabled)
Install Ubuntu 14.04 alongside Windows 8/8.1
Insert Ubuntu Live USB
Change Bios Boot order
Restart system and hold down F2
*Hold Delete button (Not backspace) instead of F2 on some systems
Once in BIOS, navigate to [Boot]
Arrow down to USB Drive and use +/- to move USB to top
Press F10 to Save and exit
Now you will Boot into Live USB
Click to install
Check 'Download updates while installing'
In the Installation Type Menu select 'Something else'
*Remember the free space we created earlier?
Select the free space then click + Sign on bottom left
*We are now going to create a few partitions
First we need to create 'Root' partition
Size: 15-30 GB is good
Type: Primary
Location of partition: 'Beginning of this space'
Format/Use as: Ext4
Mount Point: Choose the forward slash symbol /
Select ok
Create next partition by clicking + sign again
This will be the 'Swap' or 'Linux Swap' Partition
Size: Should be double the amount of RAM
*8GB of RAM would mean 16GB Swap
Location: Beginning of this space
Use as: swap area
Select ok
Create Home Partition
*click + button
Size: Fill the remaining space
Type: Primary
Location: Beginning
Format/Use as: Ext4
Mount Point: Select forward slash+home /home
Select ok
Now Click 'Install now'
Select username/password
Once Installation is complete, restart computer
If everything was done correctly, you will get the purple grub screen!
*When you want to boot into Windows, when grub screen appears scroll down to *windows bootloader and select [Hit Enter]