Having spent a lot of time questing in older campaign zones in the last few weeks, I've had plenty of opportunity to refine my BHE calling etiquette.
- When you see a big heroic encounter spawn in your instance, check your instance number on the map and call it out in zone chat, even if you yourself aren't interested in doing the encounter.
- If people whisper you, invite them to the group for an easy map transfer. Often they will leave as soon as they've moved without any further prompting. Everyone understands the purpose of these grouping requests and no further niceties are required.
- Don't bother calling repeatedly if the map already shows as full (greyed out in the selection).
- Don't bother calling if the encounter's already in progress and less than a minute from finishing - it sucks to put your map transfer on cooldown for nothing because it's over before you've even loaded in.