How does everyone got their people to master their careers? My dad (Paulo) is currently 50 and is Level 5!
Some tips...If your peep is a Lvl 1 (since occasionally you can get a Lvl 2 generated) and if you have the money for it do the following: As soon as you adopt your peep, first check the thrift store to see if there's a career manual for the room that your peep's job is in. If there is, buy it and drop it on your peep and it should be enough to trigger an automatic promotion. 300 coins really is worth it for the head start in my opinion, but the choice is yours of course.
If there is no book in the thrift shop and you have the money for it, you can buy the first promotion at 1100 coins. It gets progressively more expensive so might be unreasonable as you go along, but if you can spare the 1100 coins, you will be giving your peep a head start.
Whether or not you do the above, you should try doing the following:1. Drop your peep in their career room and as soon as it says "working on career" praise them twice with the green glove. Now wait for them to finish a work cycle (if they don't finish, drop them back on to try again, but don't praise them).
2. Once they finish, you can either let them do a few things around the house, buy them some groceries or whatever you would normally do. But take this time to check for some candy in the thrift shop.
3. Once you're ready for them to go back to work or once you've noticed them going back to work on their own, use the candy to praise them! You'll find that if you use the green glove again they will get angry and run away. From here on out, you should use candy. It takes several "years" before they will accept the green glove for praise when working again so it's easiest to just go with the candy.
4. Be a taskmaster until they are at least level 3 (or, unfortunately, if they happen to be a woman and you don't want them slacking off between babies). This means, you'll probably need to drop them into their career room and praise them with candy every time you open the game to check on them.
Optional: If you can afford it, buy the first 2 career room upgrades at least. I've managed to get Masters with only 2-4 career upgrades depending on the room/peep in question.
Hopefully these tips help. Being a task master and/or purchasing the first promotion via the book or upgrade me menu should do the trick
Good luck!