Firstly, some ground occasionally emits dazzling golden light, there will be bells hidden from the place location where the golden light appears, try your best to dig and the ACNH Items are yours. You can also create a long-term intention to bury the bells you obtain underground, and they're going to eventually become a money tree, that could bring more bells.
Secondly, you could also go fishing to get the bells, that's also a common method. Try to get those big and rare fish wherever possible, these fish will give you rich rewards. It is a good habit to visit fishing regularly, however, it will cost you considerable time. You could also choose to Buy ACNH Nook Miles Tickets. This is the fastest and many effective methods, needless to say, it costs some money. Choose from individual to individual. Do your very best anyway. It is worth noting that using bait whenever you can and preferential fishing from the ocean rather than within the river will heighten the chance of encountering rare fish.
Thirdly, If you discover that villagers often communicate in the area, this is an opportunity to obtain the bells. Give them some gifts or solve a few of their problems, they may give you some bells to state their gratitude. In addition, you can sell them some small things to get some bells, and long-term accumulation may get considerable income.