I've created couples and I've created single sims and had them go out and find partners. Nowadays I'm playing the younger generations of my existing families and my tendency is to match them up with the premade of my choice. It varies how much of a challenge I make it. Sometimes I make them join the same club as teens so they can be high school sweethearts. For my vet I went and created a pet for Liberty Lee to see how long it would take for her to bring it to the clinic so they could meet. She was the second or third customer. I'm setting up one sim to meet his future wife when she marries his sister first...
Mostly as a player I crave variety to I try not to do the same thing every time.