I'm about to try another recipe (that I make up as I go along) APA. I am having some clouding in my beer, so I got some Irish Moss tablets today. They say 1 tablet for 5 gallons. My question is, when do I add it to the boil.
If clarity is a big issue for you, there are a couple of other things you can do that may help. You are probably already doing these but just in case.
First, make sure you get a good "cold break," This can be done with a wort chiller, or (if you do partial boils - this is my method) by partially filling a large sink with ice water, then simply immersing your brew pot into it and leaving it there until the ice melts away. Obviously you need to be very careful not to splash the immersion water into the wort. The idea is to chill that boiled wort as rapidly as possible.
Second, be very careful of sediment when racking. Take as much care as possible not to suck up the trub when siphoning to your bottling bucket (assuming you bottle).
Third, if you really want to be fanatic about it, use a secondary to allow your brew to settle out even more, and again take great care in racking (I normally do not use a secondary except for some specific recipes and I am not sure how much utility in making you brews clearer this actually has, but others swear by it).
Fourth, let your bottles sit undisturbed as long as possible, thereby allowing the sediment to become more compacted and less likely to cloud your brew upon pouring.
Finally, and maybe the most obvious (and therefore, I apologize in advance for implying that you might not be doing this), don't try to squeeze out the last drop from your bottles - leave a quarter of an inch at the very bottom of the bottle. I've poured many a beer and went just slightly past the right spot to stop pouring, rendering a nice clear mug cloudy (but still delicious).
Irish moss has helped me, but all of the suggestions from SteveM are also as helpful for clearing beer IMO.
I personally pour very carefully and can usually see a very think line of yeast as it gets close to the neck of the bottle and try to stop the pour just before it hits the edge. It's usually not hard to do. I also don't care if I get a bit of yeast in my glass, but I like to practice for the sake of others who might not like a cloudy beer or the taste of yeast.
Using Irish Moss can help make the other methods of getting clear beer even easier.