Safely remove a usb device from a mac?

Just bought a mac and I have a usb air-card I use for internet but I don't know how to safely remove it every time I just pull it out I gives me a bad message. P.s. I am also try to keep my mac wireless I.E. printing and internet like I said I have a usb air-card for internet so it's sticking out of the side and... show more Just bought a mac and I have a usb air-card I use for internet but I don't know how to safely remove it every time I just pull it out I gives me a bad message.
P.s. I am also try to keep my mac wireless I.E. printing and internet like I said I have a usb air-card for internet so it's sticking out of the side and its very annoying I have heard of a few air-card routers but can I also hook a printer up to any of them. Thanks
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