I try to complete things, like my enyclopedia and museums. Have you already done all that? I also do the daily meow coupon tasks, even if I don't necessarily need the coupons they tend to get me into other things or run into nieghbors that need errands etc. Their objectives usually help me find more things to do in my day.
i look for things to complete, too. like getting all of my desired villagers, or finishing up the landscape, or earning more badges. i think about the things i left unfinished, and then i go back and finish them
I try to get all the pictures from my current villagers, even if they aren't my dreamies. That takes a lot of errands to be run which usually keeps me busy!
I try to make a good town theme. Acnl has a lot more to do than Population Growing. Making friends on here helps me play too.
Try to make your dream town. It could be an elaborate theme or just some nice pwps. Anything you want!