If the action takes place in a public space, make a good map of the area:
Choose a location that looks good in a photo or video. Are there any logos or symbolic locations that you want to be in the picture?
If you want to arrive as a group, how do you get there?
Make a plan for how to deal with traffic.
Where is the nearest police station and how quick will the police arrive?
If you intend to stay for a long time, what is the most comfortable space? Can you find a dry place in case of rain?
Think about a Plan B: in case you don’t reach the place you have chosen, is there a second-best option?
If the action takes place inside a building, try to visit it beforehand:
If it is a private building: can you go on an organised tour? Or think of an excuse to be allowed in, for instance as an architecture student.
If you can’t get inside, search for pictures and videos on-line (videos of past events, advertising or promotion images, etc.).
Get insider information (find out whether someone knows a person who works there, or ask ‘innocent’ questions to the security people when on a visit, etc.).
Make a map of the location, as detailed as possible with all the information you have gathered.
Chose a location in the building that looks good on photo or video. Are there any logos that you want to be in the picture?
Think about what the police or security will do in reaction to your action. Can they easily close down the part of the building you are in? Are there back entrances they can use?
Think about a Plan B: in case you don’t manage to get in, can you do something at the entrance?