There are a few home remedies for fleas on dogs that are very effective. A very common method is to wash your dog in dish soap and warm water a couple times a day for about a week. Another one is lemon juice and water and its also great.
Flea shampoos and flea collars are also an option. While flea shampoos have had good results for me in the past, I tend to stay away from them for the most part, especially on cats. My experience with flea collars hasn’t reaped too much results but if you have a cat that is outside all the time, this is an option. However, they can be potentially dangerous so do a little bit of homework first.