ISO primer

[boulder]

I'm understanding shutter speed settings from reading many of the posts here but I'm still a bit unclear as to some of the rule of thumbs for ISO settings vs. aperture. From what I understand bumping up the ISO will increase the noise and not affect DOF. It sounds like there are some better ISO settings than others and not sure I understand that or know which those are. I guess I'm just looking for some rule of thumbs that I can experiment with.

BTW, I can't search on ISO as it's only three letters long so I'm sorry if some of these questions are already answered.