Sophomore-year PSATs were the starting gun for my son, or at least for me to start the nervous-parent act. His scores were just on the edge of that year's NMSF cutoff. He was willing to take a couple of Saturday morning tests that year, so with his blessing I signed him up for the SAT and a subject test (on different dates, of course) and told him no pressure, just learn how to take the test (his score was respectable, but improved greatly the second time around). I think he took one blue-book test before that. Same with the PSAT. When he sat for the PSAT again, the format was familiar to him and he felt comfortable (plus, it was a lot shorter and easier than the SAT he'd already taken). He made NMSF by a wide margin, then went on to NMF/NMS. In contrast, one of his classmates worked long hours with a private tutor who "guaranteed" a 200-point increase; she raised her score by 20 points, then declared she'd had enough and refused to take any more tutoring or tests. So much for the guarantee. YMMV, of course, but imho, the best prep for the SAT or PSAT is... taking the SAT or PSAT.
Pizzagirl, if the Pizzakiddos will need to take subject tests, it is helpful to map out all the sittings beginning in junior year and try to have no more than one sitting/retake remaining in the first part of senior year. Take a look at the test dates on collegeboard.com and come up with a tentative schedule to run by them before the school year starts. They might grumble about it this year, but they'll gloat next year when their classmates are grousing about having to get up at oh-dark-thirty on the morning after Homecoming to take a stinking four-hour test! I think that spreading the testing out over junior year just makes it a bit easier and more palatable.
I also think that January of junior year is a good time for the SAT -- October and November see all the NMSFs who need to submit SAT scores for NMF status, and the hyperfectionists making last-ditch efforts to go from 2300 to 2350 before ED apps go in (I don't have an authoritative source to base this on, sorry, just a hunch). Subject tests can be taken in the fall if the related coursework is done already, or in the early spring with a little legwork and a decent test prep book. May and June are usually busy times with AP tests and finals. If an ACT is on the agenda, it's nice to know that one's offered in September.
In scheduling tests, it's important to guard against testing fatigue and allow for preparation (and greater maturity) in between. A two-month hiatus between tests may not be enough. And unless your kids have a much higher testing tolerance than mine, I wouldn't push for more than three sittings in a year.
As to college selection, yeah, it's pretty normal for the kids to be completely disinterested at this point.
I regularly put all of geek_son's college junk mail in his seat in the car. He humored me by going through it during our commutes to and from school, sometimes to hilarious effect (I love the way he says "Swarthmore"). This was how he first heard of the college he visited last year, fell in love with, and will attend in the fall.