Great to hear you are going to be using Slack - as soon as the team downloads the app onto their phone, you will have great engagement.
I work with lots of different agencies, so it will depend upon their needs as to what I recommend. Quite often, they are not using any real technology when they first speak with me so we start off slow.
I really like using Trello so I like to integrate this with Slack, however, you mentioned Asana so it sounds like this is your workflow tool.
Channels - I keep it really simple. Sometimes when there are too many choices, individuals will accidentally use the wrong channel and you then get information in the wrong place.
It will all depend upon how tasks are distributed now and what the team’s style of communication is.
I have one agency who works incredibly well with #sales, #general, #pm #bdm eg everyone in the PM team, including the VA, sees what is going on in the #pm channel. They use direct messaging quite a bit too. We have just introduced #trainingideas as part of a project we have on at the moment.
Another agency, has a separate channel for #maintenance, #leasing, #vacating, etc.
General - for all things that relate to everyone in the office ie Cake in the kitchen, Who needs stationery?, the Parking Inspector is out and about.
Leasing - applications, price adjustments, links to new properties advertised, etc
What I hate seeing is #random. So much stuff gets added to this channel that should be thought about a little more closely.
Finally, I suggest creating a simple document that outlines your expectations on how this tool is utilised. I know of some offices where the banter between team members became a bit over the top and some people were offended and it caused all sorts of problems. Here is an example to help get you started:
Let us know how the roll out goes