In my experience most clubs are started so that events that need planning are easier to plan, finance, and execute. This preexisting organization makes tournaments, campaigns, leagues, and massive battles run much smoother and have much higher turnouts.
Getting these things to go off requires some competent leadership. Without strong leadership, clubs fail. At minimum, most clubs have a president, a secretary, and a treasurer. You can expand from there.
Also clubs that have different gaming interested tend to not do so well, so perhaps separate table topers from
RPG people or have chapters within the club.
To get started you will need to find a core group of players who are well respected and willing to lead the club. Sit down with them and explain what you are trying to do and get some ideas going for the first month or two. This is the best time to start a league or a campaign and will help to drum up membership. The best way to kick off a club is with a tournament. By including the club dues in the tournament fee players can easily get started. As a store owner, you would probably need to arrange for or front the prize support until the club has a solid financial footing. (great time to get rid of those boxes of penitent engines and swooping hawks

)
Once the club is established, the best thing you can do as an owner is give them their own night or nights are their club night. In my club it is Thursday nights. We have priority on all of the tables downstairs and can ask non club members to play upstairs if the gaming area has enough club members to warrant it. This reinforces the notion of being in the club and creates a status that helps the club gain new members.
After that you should be good to go. Make sure to help the club advertise its presence and help to make any leader boards or campaign maps as impressive as possible to enhance the image of the club.
Some ideas for events are: Story driven campaigns, escalation leagues, ladder or king of the hill leagues, mega battles, team tournaments, multi-platform campaign games (creating a galaxy map and have
BFG games affect
40k games)
Lastly, perhaps something to strive for.
Adeptus Windy City is a Chicago based
40k club. They have the capital and player base to rent out 16 tables at the Chicago battle bunker every month as part of their own 11 month tournament series that culminates at their own, invite only, 4 round knockout final at Adepticon.