If your business is a GST Registrant, do not include any GST amounts paid or collected on your personal tax return (T2125 Statement of Business Activities). Claim as an Input Tax Credit (ITC) on your GST/HST Return
If your business is not a GST Registrant, include the GST paid with your Rent Expense and enter in the appropriate section in the Business Interview.
CRA Information on claiming ITCs:
http://www.cra-arc.gc.ca/tx/bsnss/tpcs/gst-tps/bspsbch/itc-cti/menu-eng.html