Starting a freestore is an easy, and most effective and radical action. There is no excuse not to have one in every city.
To start a freestore, you basically have 3 main requirements to fulfill.
First you need items. The first and easiest way is to have everyone who is organizing the freestore go through everything they own, unless they’re a minimalist, homeless, or fresh out of prison, chances are everyone can find at least one item. Then every volunteer can pester their friends and family for stuff to donate. A great source for items is dumpsters. Dumpster diving alone can keep a freestore sustainable. Flyering and calling out ahead of time for donations is a great way to get them. If you are having a regular freestore (everyone should aim for this goal) word will eventually spread and people will start donating to your cause.
Next you need people, both to run the store and for people to participate. Before your freestore, you should flyer and promote it on various social media (a facebook event is a must). Try to be a visible part of the community. Being located near busy areas is best, and bus stops are a great choice. Make sure to have proper signage so people walking by can understand what is going on.
The last thing you need is a location. Whether this is a one time action or a sustainable project will determine greatly what you need. The easiest location to secure is popup, just simply have one on the sidewalk in a busy part of town or at a local park. You may end up with some sort of police confrontation doing it on the street. If police move you, simply pack up and continue on a different block. Another option is squatting, which may end in police or building owner conflict. If you only have your freestore once a week a good thing to do is ask a building owner to let you use their space on a designated day. If need be, trade them something for the use of their building. The most likely option if you want a sustainable building is to talk to a church or some sort of community center.
If you are in someone elses building, be careful of co-option (Particularly when working with a church). A good way to confront this from the start is to have lots of banners and signs with your organization and messages on it. Be clear about who you are and what you are doing.
When putting out food, make sure to take certain items out of the package and lay them out if there is more than one serving. This way people will take what they need, not the entire box. With hygiene products you may want to only set out a small amount at a time to make sure people have an equal chance to get what they need.
Technically a freestore can function fine with one person watching it, however the more people you can get during opening and closing of your freestore the easier it will be. If your freestore is meant to be sustainable simply box up what is left over and put it out again during the next one.