What I used to do was make three or four sims and place them in town so my sim could have some choices. Usually turned out that the new sims found each other more interesting than I expected (unless I made them blood relations, of course) and they never even got around to giving my sim the time of day before NRaas StoryProgression or some other force started partnering them up with each other.
Now I have so many worlds connected in my game by way of the Traveler mod that if a sim can't find anyone who interests them locally, not even the cashier and bartender Role Sims or the pizza deliverer, then it's time to do some traveling and see what/who else is out there and single. Either that or just keep ordering lots of pizzas and see if someone else shows up. :)