My viewfinder (not LCD) has spots of dust on it. What is the best way to clean the inside? I have cleaned the outside with a QTip.
I've cleaned the inside (bottom side of prism) recently of my 30D. You can easily spot the viewfinder element when you take off the lens. I then use the same sensor swabs and eclipse fluid as I use for the sensor. I suggest you bend the sensor swab stick 90 deg so you can sweep is more easily across the viewfinder. I think I also cut off a bit of the sensor swab since it was a bit too large. It is still awkward to clean it like this though!
If it is a Canon, it may not be so much the "inside" of your viewfinder as it is the bottom of the prism, where your focusing screen is. I have a 450D, and I know that if I pop off my lens, and leave the mirror down, I can see right up to the bottom face of the viewfinder prism. I am not sure how the 30D is constructed, but I doubt that a fundamental design factor of a prominent DSLR manufacturer has changed much.
I have used a soft qtip a couple times to blot larger specks of dust off my viewfinder.