I used a flea collar on my last cocker, Sophie. I used to change it every 3 months and she never had a flea in 14 years.
I now use Frontline on Ellie, because everyone else seems to use it and the Vet recommended it, but I am not really happy about putting chemicals on her skin, although I suppose flea collars have similar chemicals impregnated into them. Saying that, I only use Frontline everyone other month from April to September and not at all in winter and Ellie has never had a flea either.
Are some dogs more prone to fleas than others?