Dating
Like in real life, Sims date and fall in love. However, sometimes that can be difficult, depending on the Sims' moods, personalities and interests. It takes a lot of work and relationship building going from the acquaintance stage and then up to friend, best friend, romantic interest and eventually girlfriend and wife. Not all Sims respond the way the gamer wants, so it takes a great deal of effort to match Sims properly.
Building Friends
Ways exist without the input of a cheat code to build friends quickly. It involves the guitar. When you build your skill high enough, you can bring the guitar to the park and start playing for tips. As you play, a crowd will gather and friendships will quickly develop. Keep playing for a certain female Sim and it's possible a romance will develop quickly from there.
Moodlets
The Sims won't want to consider romance if they are in a bad mood. They'll be in a good mood if all of their needs are met. Press "CTRL+SHIFT+C" and then type in "testingcheatsenabled true". Hold "SHIFT," click on the "Mailbox" and click "Make All Happy." Hold "SHIFT" and click the "Mailbox" again and you'll get an option to make needs static. All of the Sims' needs will be maxed out, making dating easier with female Sims.
Marriage and Beyond
Once you start a romantic relationship with a Sim, it can progress to marriage and then you and your partner can start raising your family. At that point, after marriage, your partner will become a playable character, as will the children. The possibilities are endless. You can apply the same steps that you employed to find love to help your children find partners as they get older.