To start a shakha, easiest way (at least in India) is to gather some kids, play some games like kabaddi, kho-kho (many other simple games are there also which don't require much equipment) and tell a good story from Shivaji, Rana Pratap, etc life. Slowly u can introduce dwaj, prarthana, etc. Then slowly u have to be in touch with them, know their parents, be a role model to them, etc etc.

If you're outside Bharat (Say in US, UK, etc), since Hindu population is relatively less dense, you'd either have to have good relationship with a temple or slowly get to know a few families and propose a 1-time activity (in US, we call it "Hindu Heritage Camp") where you gather kids (and family), do some yoga, games, discussion/story, etc. Later on, if feedback is positive, u can start weekly shakha.

But if you've already been to shakha, it's much easier. If you have never been to shakha, better to visit shakha for some time and get the hang of it. Then try to start on your own.

Nitesh-ji, I gave a relatively "quick and dirty" answer to your question but please email me at bsastry@uci.edu if you want further details.