Remember, the decay rate for all Relationship scores is 2 points per day. If Sims don't spend regular time with a friend, the relationship will eventually fade below the friendship threshold.
Sim Neighbors are Smarter
Sim neighbors are smarter than the Sims you control in the active household. Visitors always choose the best activity available to raise their mood, unlike your current Sims, who choose randomly from among the top four.
Start With Several Sims
It's more difficult to start with one Sim than several. Even if you do not intend on keeping all of them, start with as many as possible and start them working. You can kill them off later when your career stabilizes and you have the necessary equipment to get motives up quickly and work on skills. It is generally a good idea to keep at least two Sims so that they can keep each other's Social Motives up.
Neighborly Relations
To raise Relationship points with a neighbor that your Sim doesn't like, prepare a group meal to eat with the neighbor, watch TV, dance at the stereo, play chess, use the hot tub ... Click on the neighbor and have them "Join" you. The relationship with the neighbor will go up without any of the negative reactions that occur in regular social interactions.
Hug Until 100!
Never let Sims choose their own social interactions. They make horrible decisions. The best way to build up a relationship with another Sim is to talk until the relationship is at about 30. Compliment until 60. Hug until 100. If possible, do not fall in love -- it can bring down the social motive when jealousy occurs. Just make friends and send them on the way.
Sim Personalities
Choose your personalities to fit the role you want your Sim to play. Neat Sims make very good stay-home cleaners. Outgoing and Nice helps a Sim looking to make family friends. Playful makes the wonderful interaction "Entertain" available more readily. An Active Sim is suited to be on-the-go and doesn't get uncomfortable easily.
Will You Marry Me?
When trying to get someone to marry you, there is a sure-fire indicator of his or her response. If you kiss the person and receive a passionate kiss, they will say yes. A polite kiss means you will be turned down.
It's Difficult Making Friends
It can be difficult to make friends when first starting out because there are not very many Sims in the Neighborhood. When first starting, it's generally a good idea to move in eight Sims with high Outgoing and Nice points into every lot. You can evict them later when you want to move another family in.
Outgoing Attributes
It is recommended to always max-out a Sim's Outgoing and Nice attributes. Maintenance of Social Motive is extremely difficult without these attributes (and impossible in cases when there are no Outgoing and Nice points allocated). With these maxed-out, it will make it easy to build a relationship to 100 the first time you meet a Sim.
Get Those Social Relationships Up
A two-member Family is the best size to keep your Sims' Social up. A third member of the family might be good to manage household chores and procure friends so the other Sims can focus skill building and maintaining a positive mood.
Roomy Relationship
Room score can have a big impact on how relationships go. Lights help this a lot. The $350 floor lamp is one of the best, most-cost efficient things you can do for Room score. Also, always make rooms in which you plan to be social or gain skills very large. Rounding of corners with a few diagonal walls will also help.
