Dual Citizenship is common in Canada. There are no specific requirements; however it is recommended you use your Canadian Passport (once obtained) when entering back into Canada. Please note if you did show up at the border with your UK passport and Canadian Citizenship Card you should not encounter any problems.
Please visit Citizenship & Immigration Canada for more information on Dual Citizenship:
To apply for a Canadian Passport please visit: www.passportcanada.gc.ca.