Hey i was just wandering if you can boot from a USB
Yes you can boot from USB mediums, as long as the laptop/computer supports booting from USB.
how do you tell if you can? and if so how do you do it?
There will be an option in the boot sequence of your BIOS ... USB-HDD or something similar. Would help if we had the model number of the motherboard you're using.
One of the more popular tools for creating a bootable usb is the HP USB Disk Storage Format Tool.