Ok people, your babies are little. Especially you with the 12 week old. I certainly wouldn't expect a 12 week old to self settle.
With dd, I would put her down asleep then work backwards until she was awake and try and leave the room for a minute or two. If she grumbled, i would leave her and she'd sleep. If not, I'd go in and rock. This I started at around 6 months and she naturally got there. At 20 months, she's had plenty of regressions - in between 6 and 20 months I've had to go back to rocking. But I don't mind as know it won't be forever (she isn't my first).
I do remember that it takes longer to rock them to sleep if they're overtired. They trick you into thinking they're not tired, when actually they are. So try earlier bedtimes.
Also pick up put down is a horrible technique (did it with ds, stopped after 2 nights).
You can do gentle encouragement towards self settling, just appreciate that 1) you won't be doing it forever and 2) sometimes baby will just need you a bit more some nights more than others.
I admit I would sometimes tear my hair out with dd and ds not settling but once I relaxed a bit with dd, she's been so so much easier!