I agree, get it on-grain add a couple of pins to hold it, then as many more pins as I think necessary. That depends on the paper/tissue, the fabric and the shape of the pattern piece. I usually try to get a pin near to each notch - and I cut the notches outwards. If you cut inwards you are loosing any leeway to let out if necessary, and if you just snip they can disappear - remember the jackets on the last seried of GBSB that had two left sleeves! That happened because they couldn't find the notches snips and the fabric was more or less the same on both sides.