easy answer: collect supporting votes, e.g in a tmo thread. As soon as the number of supporting users exceeds a certain number (e.g. the total number of valid votes in last council elections), council is supposed to organize a referendum.

/j

[edit]
usually you publish a decent letter of intent on the issue, then supporting users can "sign", like
...or some similar but better worded and thought request.

[edit2]
since Estel mentioned to me that many people might have misconceived this post, here a clarification: this post is not meant to support any riot destined at directly removing any council member. Au contraire! It describes the general procedure to introduce requests for reasonable improvements or changes to rules, as practiced in virtually all democracies. Nobody would think such a procedure as described by me would have any chance to pan out for idiotic requests like e.g. all women aren't allowed to wear any clothes in public anymore ;-D. However common sense is that common sense will kill those idiotic requests in the stage of collecting support. And in the end it's the administrative entity that will reject requests that are against any of the valid rules aka laws - that's why a request to shoot politicians never will result in executive doing that (usually), despite I might imagine such a request often finds a lot of support ;-)