I try and post once or twice a week, and people love photos. I choose and cake I have photographed nicely and give a brief description of the flavours, the event and sometimes the background behind the design of the cake. If I haven't had any decent cake photos (or I didn't like any of the cakes that week, as in, I wouldn't want to repeat doing it!), I take a photo of the cupcakes I have for sale that day or something.
I also post upcoming classes I teach.
I hate being bombarded by business's posts myself on my personal page, so I don't post more often on my business one to avoid being the one doing the bombarding!
ETA that a way to get more "likes" is to run a give away of something. Just be careful to read the rules FB has to avoid getting your page shut down. Be aware that more likes/fans does not mean more cake business necessarily - most of my business is through word of mouth, although I do find it works for advertising my classes. I guess I am followed more by bakers and decorators, than by cake customers.