it would be good to at least have both samples in the same key, they would blend better that way right off the bat, if you have to do tuning though, just write out the scale of the original samples key, then write out the scale of the second samples key, and adjust each note ( on your paper) up or down a semitone and see what it gives you.
all scales have a relative major or minor too.
read up on this.
https://en.wikipedia.org/wiki/Relative_keyyou wont learn it overnight, but with practice youll get better. its hard enough finding the key of the sample your in in the first place imo, but ive found that after a year or so, i can sometimes tell when two songs are in the same key.
it seems to happen alot when im listening to the radio or something, the chord progression or will remind me of another sample with the same notes, although finding the actual key out is a little harder.
good luck.