I usually just talk to my coworkers in Slack. There are also ways of talking to slackbot. For instance, you can ask slackbot to remind you of things. Here is the structure of that kind of request:
/remind [who] [what] [when]
I can use this to set a recurring reminder for myself.
/remind @jbranchaud Drink a beer at 5pm on Fridays
Slackbot assures me that my reminder has been noted.
