When I changed my belt no one gave me these tips. And the book was also not much help when it came to these. So, here are the tips, the rest you can get from the book:
1) Parts that no one seems to mention you should purchase while your into this: A) I highly suggest the belt with the timing marks. B) The time belt cover has a neoprene gasket at the bottom center. This must be purchased separately. But no one tells you this. The old one will be highly distorted when are removal and will not have a nice fit for reassembly. C) Oil pump o-ring. Your oil pump is probably linking and if it not, it will start to shortly after you complete this job. To replace this o-ring you must do almost 80% of the same work, so buy the ring and do as part of this job. (It totally fries me that neither the book (which is the reason I purchased it), nor the guy at the Subaru parts counter - makes these suggestions. In fact, the parts counter, not making these suggestion taints my faith in my Subaru dealer.
2) When it comes time to unscrew the harmonic balancer, (on my 1999 Outback), there is a rubber plug just behind and below the throttle body. Remove the rubber plug and you'll see the flywheel or ring gear assembly. Spin the engine until you see a notch or hole that you stick a large screwdriver in. This will hold the engine in place while you break loose (using a breaker bar) the bolt on the harmonic balancer.
With those tips, the job goes pretty smooth and you'll be much happier when you done.