Rotational player here. In my neighbourhood, I only have a few single Sims. If I do have them, I usually use the LTW as a guide on what kind of Sim I want them to be. If I am not following the LTW, I would either let them open a business, be very passionate in their hobby/interest or mess around their neighbourhood (this is for Romance sims who aim to mess around with as many ppl as they can). There are many ways you can do it, these are the ones that I have done in my current neighbourhood gameplay!