Thats not a easy one.Iv had chances to steal cigs before but i never took the chance.
Best way is to find somewhere that sells them in behind the counter.Get friendly with the shop staff so that it builds up trust and some of them go out back for a cuppa and ask ya to keep a eye out for them why they go take make a drink or go to toilet.Thats when u can grab cigss
Or wait untill no one is at the tabacco counter and quickly take some and run.