Sit-ins are usually unannounced and planned in secret. Blockades include blocking doorways, roads, or movement in general. Small blockades are usually planned in secret, while a large blockade may have to be announced in advance. Occupations are essentially mass sit-ins, which are most effective when planned in secret. To make sure everyone in the group will react the same way, work out various scenarios that could occur and how you'll handle each one.
Weekdays are best.
Support people do not get arrested and are responsible for taking care of things like media, transportation, supplies, bail, legal problems, and caring for the children or animals of those in jail. It's best to work out a timetable with a list of all the jobs you need to get done beforehand. Delegate work to volunteers, but keep track of what they're doing. If possible, one person should be assigned to do media work and nothing else. There's little point in getting arrested if no one hears about it.