The general rule of thumb is to match the sequence frame rate
to the majority of your source material and allow Premiere to
interpolate the odd fps clips in the timeline instead of tweaking
frame rates using Interpret Footage.
There are occasional exceptions that might require
individual clip-by-clip treatment for fps conversions.
The general rule of thumb is to match the sequence frame rate to the majority of your source material
I would disagree with that only because PP is just not very good at converting 30i or 60p down to 24p. However, going from 24p to 30i or 60p works fine. So I think the better general rule is never use a 24p sequence unless ALL the footage either is or will be Interpreted as 24p. If you have ANY footage that is not 24p, then use 30i or 60p as appropriate.
I have not really worked much with film or premiere, so would you mind explaining what you mean by 30i and 60p? I'm sorry!
Those are shorthand designations for both the frame rate (24, 30, 60) and either interlaced or progressive scanning (i and p).
So 24p is 24 progressive frames, the 'norm' for film and digital cinema, also an option for video.
30i is 30 interlaced frames, the norm for NTSC and one option for HD.
60p is 60 progressive frames, one of the options for HD.