I've always had trouble making a good list at 1500 points. For some reason, pushing out to 2K always gets me to a far more lethal list. Regardless, a few suggestions I've picked up:

Pathfinders: at 12 points each, pathfinders are incredibly worth it. The problem is, they have the overpriced 80 point devilfish requirement. So as long as you're paying the price for the devilfish, max out your pathfinders. At 1500 points, it's asking a lot to run two squads, but that's why I keep talking my friends into 2K games.

Remember the marker beacon on pathfinder devilfish. With this equipment, you can bullseye a deep strike just over half the time. Something to consider when facing armor, a STR 10 shot into an AV 14 is not as likely to penetrate as a STR 7 into an AV 10. Using that marker beacon, you can chance deep striking a team of crisis suits into a thin strip of open board behind an opponent's armor and their board edge. Can it go horribly wrong? Sure, but it can also pay huge benefits if it gives you access to places on the board your opponent isn't prepared to defend against.

Another thing I've had to spend a lot of time looking at is how to maximize what you get for the points you spend. One key example: Shield Drones cost you 15 points each. For that, they come with a 4+ invul, and an armor save of whatever unit has the drone controller. So, for those 15 points each, they can have a 3+ armor save if with an XV8, or if you get them on XV88s, for the same cost they get a 2+ armor save. For this reason, I never take Broadsides without shield drones, you just get so much more for the points. When a dreaded STR 8 or higher shot comes in (which would normally double out a suit), it goes right on the shield drone, and if it wasn't AP2 (hello, Leman Russ Battle Cannon which loves to reliably double out whole squads of XV8s) those hits all save on a 2+. My advice, XV88s draw all kinds of fire. Shield Drones make that unit very sticky, even just two.

Last item for now: kroot. The biggest issue you'll run into with them is they break and run easily. But really, for the points, they're still pretty damn good. And when you bring enough, you get a tremendous volume of attacks. One of my favorite units is the 200 point kroot mob - 16 kroot + shaper and 10 hounds. Their shooting attacks are STR 4, and within 12", you're doubling the number. And if someone assaults you, the hounds hit at I5, and then you can take all the I5 and 4 return wounds on them, so you still have all the kroot available to hit at I3. And to add to all this, they're scoring units if you can keep them around. Just tuck them into cover, and they're one of the few Tau units that are really worth the points you spend on them. At 1500 point lists, you're probably going to want to create smaller units, so just keep in mind that a 100 point unit of 10 kroot and 5 hounds will make a morale check if it suffers 4 losses in a single round of firing, and is rolling that against a 7. So keep 'em in cover, and don't be afraid to go to ground to keep them around.

I started playing 40K about a year ago, and have played only Tau until just a couple weekends ago. Good luck to your buddy, and here's hoping for an update sometime in 2012!