How do I mention users and tag channels in Cliq?

@mentions and #tags are used to notify users so that they do not miss out on important messages.

@mentions are used to refer and notify a user in a channel. Mentioning them indicates the user to join a conversation or share something interesting about a topic.
#tags are used to refer to another channel in a chat.

Mentions and Hashtags	Purpose	Restricted Permissions
@all	To tag all participants in the channel	✔︎
@available	To tag all participants whose status is available.	✔︎
@username	To tag a specific user	✔︎
#channelname	To tag channel for referral.	✗

@mentions

If a user within the organization is @mentioned in any channel (i.e. Organization, Team, Multi-team, Personal, and External), then that user will receive notifications.
External users can be mentioned only if they are a contact. However they will not be notified.
If the user is not part of the channel and is @mentioned. A notification will appear on the chat to add the user, but the user will not get the notifications sound.
To know more on @mentions refer here.

#tags

You can #tag any channel (i.e. Organization, Team, Multi-team - open channels) even if you are not a part of it.
However, you cannot tag personal, external channels or closed channels in a channel chat.
When you type # in the channel. A list of channel suggestions will appear. You can choose any channel or type the name of the channel to #tag it.