I've heard different ways of getting Exotic Shards from dismantling Exotic weapons and gear, but it was all year one. Has it changed since then? I don't want to make a stupid desicion and waste my exotic.
Dismantling a brand new exotic grants one shard.
Dismantling an exotic that has had enough experience/motes dumped into it to unlock all the perks will grant 2 shards.
For effective shard farming, buy a heavy exotic weapon from the kiosk. Pop a heavy weapon telemetry from the gunsmith. Equip the weapon. Burn 6 motes to level it up, do not purchases any of the nodes. Dismantle the weapon. Get 2 shards. Repeat until you are out of glimmer.