There are lots of ways to promote a product, especially with the ease of access to digital marketing. Nevertheless, as a marketer, one of the main objectives, if not the main, is that all initiatives should aim to start word of mouth.
Word of mouth is simply people talking about your product, hopefully in a good light. It is people recommending you to their family, friends, colleague, to their network. Before, word of mouth is only verbal. Today, there is already online word of mouth-- social media posts, videos, live streams, etc. So how do you make people talk about you online (and offline)?
One key is to get creative. Retailers are slowly turning their stores into Instagrammable locations. Restaurants have turned their food Instagrammable with creative platings, and online sellers are maximizing Facebook and Instagram live for promos and events. But of course, your product has to be good as well so people will be happy to talk about it.
Now if you do the examples I mentioned, it might take time for you to build a really strong word of mouth, so sometimes, tapping influencers is key. Influencers may be online-- those with several following on social media, or offline like authors and speakers. When they talk about your product and their followers and listeners know about it, there's a higher chance of word of mouth.
Lastly, (but definitely not the last thing you can do, there are lots, but I want to make this short and sweet) is to plan strategic content that triggers emotions, that can lead to the content being viral. It can be short films, songs or jingle, memes, etc. If it's trendy and triggers emotions, then the more likely it will be shared.
Of course nothing still beats excellent quality partnered with a reasonable price tag. If people are happy, they can't help but talk about it!