Ok some like the museum shop requires you donate a certain number of insects, fish i think it was 20 of each, and at least one real painting, after that' you speak to blathers daily and he will tell you his problems and suggest opening a shop.
Go and speak to Isabelle for projects.
Once you unlock the museum shop and donated about 40 of each insect, fish speak to blathers again daily till he reveals opening coffee shop.
Others require you to obtain town perfect status or just animals randomly approaching you asking for this.
you can start by completing a few of the town projects already available







