Awww, ADFs are so cute! Lots of fun to watch! I have a couple, but none with bettas at the moment.
I highly recommend this site for info:
Flippers 'n Fins. Check out the FAQ and the care sheet. Very helpful message board as well.
One of the biggest concern with keeping ADFs and bettas together is making sure that the little froggers get enough to eat. They have poor vision, and hunt by smell, which makes it easy for an opportunistic betta to steal their lunch. You can try feeding by using an eye dropper or turkey baster to dangle food right in front of it, or by separating the betta in a breeder's net or something at dinner time. Another thing about food - mine will *not* eat anything but frozen foods (mostly bloodworms, sometimes brine shrimp). They totally ignore the HBH Frog and Tadpole bites that I got for them...
Make sure that if you need to medicate the betta that you separate him from the frog first. Frogs are very sensitive to medications. Aquarium salt is also not recommended. Also, make sure that your lid is tight, and all holes are covered, as they are at least as good as Bettas at jumping out of their tanks. With any caves or hiding places, make sure their aren't any holes that they can get stuck in, and that there is easy access for them to get out - hollow ornaments are dangerous unless they can get out the top - they aren't really smart, and can get stuck inside and unable to get to the surface for air.
That's all I can think of for now... Have fun with 'em!!
Stacey