When you right-click on your desktop and get the little context menu it says to use alt-a or alt-d to select activities, but neither of those key combinations do anything. What shortcuts are available? Minimizing my windows and right-clicking on the desktop every time I want to access activities is proving to be a bit of a drag.

Meta+Q - shows activity manager
Meta+Tab - switches them

Cheers

These are not global shortcuts, i.e. some part of the desktop has to have focus for the shortcut to work. You can assign a global shortcut by clicking on the Tool Box ("cashew") -> Shortcut Settings -> Activities... -> Global.

There is also the default global shortcut Super/Meta + Tab (usually Windows key + Tab) which switches activities. You can change it in System Settings -> Shortcuts & Gestures -> Global Keyboard Shortcuts -> KDE component: Plasma Workspace.

Thanks, guys!

Is there a possibility to use hotkey to access a given activity? Just as in the case of desktops within activity. Eg. I have 3 activities and I want to assign Meta+F1, Meta+F2 and Meta+F3 to them. Is it possible?

Same question.
Without ability to set hotkey to each room all this activities things looks useless to me.

There are various workarounds available to set hotkeys to certain activities on this forum.
See viewtopic.php?f=67&t=95623&p=201390&hilit=qdbus+activitymanager+activityname#p201390