There are many ways to make a working Bootable USB mac osx installer...
I'll start with the Windows Tut...
1) Downloads: Download PowerISO.exe link removed No link.... No warez --Lacedaemon
2) Installing: Install poweriso, it's crack
3) Bootabling : Click on Open and select your DMG or ISO file then click on tools--->Create a bootable USB
4) Device: Select your device to install it on
5) Start: Click on Start and wait until it finishes ( for 4.5 GB it takes about 3/5 minutes....)
6) Finish!: Congratulations! Now you have a bootable USB media... please if it won't work by selecting F12 at boot prompt, modify the BIOS to boot the USB before everything!
2) ONLY IF ABOVE WON'T WORK!
1)File -------> open ------> select your dmg/iso file
2)Right Click on usb device ------> Format with disk image and select your disk image
3) Start format and wait...
4) You now should have your mac osx bootable USB!
Mac... It's Easier
1) Programs: Open Disk Utility
2) Selections: Select the USB you want to make bootable
3) Clicks: Click on Erase -----> Format: Mac OS Journaled Name: whateveryouwant
4) Wait: Wait until it finishes erase....
5) Selections: Click (on the left) your USB media you have just formatted then click Restore
6) Clicks: For Source: Click on Image and select your DMG or ISO image For Destination : drag the USB media from the left to the textbox
7) Clicks: Click on Restore and wait..... it may take up to 10 minutes...
8) Finishes: If you note that your file isn't bootable then download chameleon bootloader or chimera one and install it (with all customizations you need ) to your USB media....
Hope it helps!
Don't hesitate to contact me!