Strategies
Build Friendship as quickly as possible: one of the biggest problems that you are going to have with your Singles is that they get embarrassed when their roommate(s) see them running around in a towel or naked. You probably don't care, but they do. So build those relationships at least to the point where they will use the toilet while a roommate is in the bathroom at the same time. At normal relationship decay rates, it should take three or so solid days of maxing out the Friendship meter before the long-term relationship gets to the point where they aren't embarrassed. Once this happens, you'll find it much easier to have them go about their daily routines.
Build Erotic quickly: all of the apartment layouts include 1 decent-sized room and 2 smaller rooms. The decent-sized room should be big enough to hold a double-bed (it may take moving a couple of doors around in the Penthouse, but it can be done). Once you get the long-term Erotic relationship built up to the point where two of your Singles will sleep in the same bed or at least share a bedroom, you can turn the third bedroom into a study or TV room or something like that. At normal decay rates, it will take three or four days of maxing out the short-term Erotic meter every day for the long-term Erotic meter to reach the point where this can happen.
Share the chores: there is nothing that will cause a blow-up and argument faster than one or two Singles who aren't pulling their weight when it comes to chores. Bathtubs, toilets and tables have to be cleaned, food has to be cooked, dishes have to be washed, the apartment has to be vaccuumed, trash has to be taken out, and broken appliances have to be repaired. I'd recommend that everyone cleans something at least once every couple of days (once a day if Ellen is one of your characters) and that you rotate repairs.
I've found that the following system works pretty well:
whoever cooks, cleans the dishes
take the trash out on your way to work (once the "go to work" window opens, take out the trash and then go to work - the Single will just stay at the bottom of the stairs until the workday finishes) - make sure that you rotate it
split the cleaning - one cleans the table, one cleans the toilet, one cleans the bathtub
rotate the vaccuuming - Singles will sometimes just do this on their own, but try to split it fairly
rotate the repairs - keep a strict rotation on repairs; something may get away from you every once in a while, but keep the rotation going
Watch out for jealousy: when two Singles have a decently strong Romantic relationship, jealousy can rear its ugly head. If not addressed quickly, it will result in a blow-up argument and possibly a break-up (you ain't dipping into that cookie jar no more). Jealousy happens when one partner sees the other Flirting or Romancing with another Single. If the long-term is pretty well maxed out, it doesn't matter whether the other partner started it or is simply being hit on by another Single; any Erotic or Romantic actions between the other partner and another Single will do it. So if you think this might be a problem, do your chatting up out of the sight and hearing of the other partner. Being behind a closed door works pretty well, as does going to the bar by yourself (of course you lose the "invite to bed" option at the bar because there is no bed to use). Surprisingly enough, Singles know when the other half of a double-bed is occupied, but they never come in to see who is occupying it.
Learn to slack before taking the promotion: all told, you can get five promotions. This will result in an extra $500 per day in income, but also an extra 90 minutes in the workday. Every point spent in slacking reduces the workday by 30 minutes. So expend a point in Slacking, then take a couple of promotions (you're still even), then more slacking, then another couple of promotions (you're still even), etc. When you're maxed out in both, you're still 30 minutes to the good on the workday.
Replace that crappy second-hand stuff as quickly as possible: first off, second-hand stuff breaks more quickly than the other stuff.This means that you're going to have to be rotating the repairs more often. Secondly, the second-hand stuff doesn't work as well as the new stuff (more than an hour to fill your hygeine meter in the second-hand shower, about 30 minues to do it in the designer shower). Although I must point out that no matter what you do, the bathroom sink seems to break about once per week, regardless of the quality.
Points in cooking/cleaning/repair mean more time for you: just that. The less time you spend cooking, cleaning and repairing is more time that you can spend chatting up and hitting on other Singles.
Keep those need meters filled: this is where you're going to get your experience points (and levels) from. The better you can satisfy your Singes' needs, the faster they will gain levels and skill points.
Minimum Relationship Levels Required for Activities: most interpersonal activities require a minimum long-term relationship level with the other person before you can engage in the activity. Here are the default values:
And just in case you were wondering about the effects:
Oddly enough, the game is set up to allow you to call your office (it knocks a couple of points off of your "Fun" meter), but I've never seen it on the phone menu.
More to come as I think of it or stumble across it.