Doing stuff and talking to people gives you topics. You can use these topics when talking to people and they'll gain exp in a subject. When you reach 100% in the right subjects (such as social media and fashion) you can encourage an interest. Once they have the correct two interests, there should be a way to change their AT, which is basically a lifestyle change.
So for example, if you're just starting out, you need to get Diane more physically fit and into social media iirc. You'd want to work out and post on facebook to get topics, then use them when talking to Diane. But there is one catch in that she already HAS certain things she will want to talk about, will be offended to talk about and things she's kinda whatever about. So you need to have two things she likes talking about to match one things she's neutral on and THAT will let her get exp in that subject. In this case, you'd be doing something like talking to her about your chores or handing over some fitness magazines, then for a final conversation you talk about facebook.
Progress is slow at first. Just keep doing stuff and talking to people and it'll speed up. Or you can use the cheat mod to speed things up a little (such as by giving yourself money to spend on gifts or give yourself a level or two in some skills that increase how fast you and everyone else levels up) without breaking the game in half, which is what I personally recommend. I'm more generous to this game than most, but even I think the beginning section is a little frustrating in how much visible progress you make.
