Vintage Synth Repair

hi folks, i just want to double check something really quick....

i was probing recently with my scope, and got a spark as i made contact w/ a leg. i want to check my "scope technique" before a new project.

when i have had to use my scope(not too often), i generally connect the NEG probe to ground, and check w/ the POS probe. is this generally suggested? or, say for instance, if i were checking a waveshape output of a chip, should i be picking a ground point closer to where im trying to read the signal?

i know this is really daft. i just want to definitively know im going about this properly. thanks-rj