There are a number of different channels one could use to advertise. The key is to choose those that are used by your customers the most. This could include online channels (like Facebook and Google search), mass media channels (like Radio), and physical channels (like Posters in Store).
Paid advertising is a good option to use, but only if there is the budget for it and if there is a very clear and targeted approach with a strategy in place to analyse and measure the results. At this point we will not be able to cover this type of advertising.
However, there are tons of free/ low cost ways to create very targeted and effective advertising.
Examples
Facebook groups
Whatsapp groups and friends
Give existing customers an incentive to participate in the promotion and pass the advert along.
Include it in your email signature.
In Store Posters and flyers
Flyers in Postboxes in a specific geographic area
Flyers at traffic lights
Gumtree ads & Facebook marketplace
Set up a shop at a local market or at an event at which your ideal customers will be and hand out flyers as they buy from you or as people walk by.
Have a stall at a trade fair or convention.
Join a Local Meet Up & Networking groups
More examples:
https://www.thebalancesmb.com/low-cost-marketing-ideas-2948325 Elite Chess Example
With Elite Chess, we decided to use Whatsapp and Facebook because these are the channels which all the club chess players use in South Africa. There are numerous chess groups on both Facebook and Whatsapp which Coach Dione is a part of. So he simply just advertised the promotion there.