The Bow Biz website has some photos and a short video showing some good methods of placing dog bows.
How To Put In Dog Bows : Dog Bows, Quality Dog Bows - Yorkie, Maltese, Shih Tzu - by BowBiz
I like to use the little latex free bands to put the topknot in with. You just snip them out when you are ready to replace them. you can get 500 of them for about $6.00. The latex free do less damage to the hair.
Amazon.com: Latex Free Dog Grooming Bands by...
Once your band or bands are in place you can more easily place the bow. But if you are using a clip on always make sure you are always near by while your baby is wearing the bow. Your dog could still manage to get it out and the bow can be a choking hazard.