If you want to use the flash the "most effective way", it makes me think you are trying to direct the most light on a subject as possible. To do this you would want to point the flash directly on the subject and possibly use a snoot depending on the distance away from the camera.
If you have a white ceiling that isn't too high, bouncing requires no additional equipment beyond the 430EX and provides a much larger surface area for the light to reflect off of. This is typically much more pleasing as the light is softer and more attractive if it comes from above and not directly head on.
I don't think the question is, what is the most effective way to use a hot shoe mounted flash indoors, the question should be something like
- What is the most flattering way to light a subject indoors with a flash unit
- What is the best way to light a macro subject indoors with a flash unit
- How do I best photograph large groups indoors with a an on camera flash unit
- etc. etc