The best and most obvious way to help Monero is to actually work on the source code of Monero to make improvements and fix existing issues. Those with coding skill sets can head over the Github page and poke around to learn more about the inner workings of Monero.
Other than coding on Monero people can also make their own applications for Monero. Make a newer, easier to use wallet. Create a point of sale application that accepts Monero: Develop a game that uses Monero to unlock in game purchases, etc etc.
Monero is unique from most other cryptocurrencies because it has no central organization or team in control of it. As a result of this, people who choose to work on Monero can sometimes put up funding campaigns that the community can fund to continue to grow Monero. These campaigns can include major code additions, validating new code that has been added, building wallets or other services, and creating material to hand out to people. There is no limit to what someone can request.
Consider hosting a meetup at a local bar or cafe to teach locals about Monero. Becoming more of an expert while building a community who support Monero’s Growth!
Existing businesses can start accepting Monero right now.