I leave mine to dry out over the fall directly in the garden. The cats climb right in, munch the stalks, and roll around in it. In the
spring, I cut it right down to nothing, and it comes up again. If you do want to snip tho, I wouldn't think it would be a problem to snip anywhere, as it seems to grow like a
weed.
You can also try "catmint", which is a bit different, and self
seeds readily.
Side note - this year I tried a packet of
seeds that included catnip, cat grass (2 diff. varieties, and something called "cat lettuce") The cats think they've died and gone to heaven!