You can buy the tips from lots of places and they're relatively cheap to ship.
The solder tips for Hakko 936 (the 900M ones) will work with the fx-888 the only difference is that the new ones are a few mm longer I think. Just be careful if you order 900M tips, a lot of such tips on eBay are clones made by various companies and don't have the same life as original tips and often they also show up in stores like Amazon.
The shape of the tips, you can see here:
http://www.hakko.com/english/products/hakko_fx888d_tips.html#productNavThe page also has for each category a "how to use" link and shows examples, so you can determine what's best for you.
If you have the money get the kind that has a small hole in the center.. ..so you can put flux on board and then put some solder in the tip hole at the top and just drag solder like it shows in the how to use page)
The D shape that looks like a regular flat screwdriver is also often useful. The K is also nice for surface mount stuff and for breaking solder bridges and for drag soldering
I would recommend getting a small size (but not the smallest, often not worth it) and one of the larger sizes from each type but it depends on how much money you have.
There's also an eBay distributor for Hakko which sells from US... seems reliable and doesn't look like selling fake stuff :
http://stores.ebay.com/NEI-Lamps-and-Electronics Scroll down and click on Hakko soldering tips.
I would also suggest looking at Sparkfun or Adafruit (both in US) and maybe tequipment from Australia I think (and I think they also offer a small discount to eevblog members) :
http://www.tequipment.net/hakko/soldering-equipment-1/tips/