How do you make a shed into a club house?

I can only offer advice in general terms, as you have not given any details. 1. make it weatherproof - especially the roof - else anything you put in there will get wet and/or mouldy. 2. insulation - if you plan to use it in cold weather, then fiberglass blanket (loft insulation) on the inside of all walls and the roof, with some sort of covering (hardboard or cardboard) to keep those itchy fibres in place. 3. ventilation - you cannot seal the shed completely and expect to keep breathing - this will also keep condennsation (humidity) under control, to prevent mould or rot. then you have other things like power and light, if you want them - be VERY careful if you are thinking of any sort of gas or paraffin heating or lighting - you could either have a serious fire, or gas yourselves with the fumes.

It sounds like you have ideas just don't know what to do with them. Assuming a 10' X 12' older metal shed. 1} You might want to support or brace up for stability. OK is there a construction site anywhere near you? How about someone doing a home renovation? These are the best places to get wood and other stuff. If your going out to a construction site "ONLY" go to the trailer, or the first trailer. Be respectful and ask for scrap lumber and materials. They might ask you to come back after quiting time, because you or anyone that doesn't have business with them is not covered under the insurances. I know the trailer I mentioned that's where I would be. Im an electrical contractor and no advise on installing electrical in the fort. Battery operated stuff ok? So as your going to school or around town keep your eyes open for construction sites or houses under remodel. When you do get the wood to brace it remember straight up and down is never as strong as diagonal. Brace walls corner to corner. I'll put this on the clipboard in case you have another ?