Surbier, for a start you might find this helpful- it is the only ALS tutorial that I know of that provides several clear graphical examples. As does the author of that tutorial, I also find it easier to think in terms of ALS Chains since the construct of the ALS xz-rule (2 ALS sets), ALS xy-wing rule (3 sets) and ALS xy-chain (>=4 sets) are all the same- the only difference is the number of sets and restricted commons:

http://www.sudoku.org.uk/SudokuThread.asp?fid=4&sid=10326&p1=1&p2=11ALS Chains are in a category that I call Pattern A solving which refers to pure, visible, 'what is' patterns such as naked pairs, xy-wings and the like (as opposed to Pattern B solving which refers to the nice loop & AIC chains). Over the last year or two I have been concentrating on manual solving only puzzles at the > SE=8 level, beyond the SSTS point (Simple Sudoku limit) which, for me at least, don't lend themselves easily to pencil & paper solving, but lately I decided to take some time out & go back to my collection of Los Angeles Times Diabolicals (usually SE < 7.4) and 'refresh' my basic method Pattern A solving skills & for this situation, I find that pencil & paper works just fine.

IMO, ALS Chains are the most powerful method available for this type of solving (one reason being that in their most powerful form, they are much like grouped nice loops or AICs), but I find they are more likely to be both useful & reasonably easy to find in end-stage solving when there are likely to be more bivalue & trivalue cells. It's easier to explain my procedure with some graphics. The following is from a real-world solution of the LA Times diabolical from 04/15/07. In this case, two 4-set ALS Chains broke the puzzle:

The graphic is pretty self-explanatory: The ALS sets are distinguished by colored cells and the black lines show the connection between the restricted commons. The flanking pink & green sets 'point' to & thus eliminate the 2 in r2c9. One would think that finding a 4-set ALS Chain (aka ALS xy-chain) might be difficult using only pencil & paper, but it actually isn't if you practice a lot. Often, since this can be the most strategic point in the solving, I will first make a copy of the puzzle to work on since I'm going to be marking up the puzzle quite a bit. I start by circling with light pencil potential sets, particularly those where there are 2 bivalue cells in which only one digit is duplicated (as opposed to almost naked pairs where 2 digits are duplicated) because it is going to be easier to find restricted common connections with these types of sets eg. the green, blue, and pink sets above. Next I circle almost naked pair sets such as the orange set above (couldn't find an easy way to circle the set in the graphic

).

Finally, I isolate other sets that might be useful such as perhaps the set in r3c46 (2,8,9), but here I draw a square around them. Now I am able to look at the puzzle and see the isolated sets & see what I can make of them. It takes a bit of practice to decide which method works best for you, but if you understand the underlying principle of ALS Chains and find the best way of isolating potential sets, you find that they start to jump out at you even with pencil & paper. If you get to the point where you can find 4-set chains, then something like a 2-set ALS xz-rule will be a piece of cake!

The final ALS Chain above which totally dismantles this puzzle is a good example of why I first start looking for 2 bivalue cells where only one of the digits is duplicated. Because in these types of sets there are 2 single digits such as the 2 and the 5 in the blue set and the 1 and the 9 in the pink set, it is more likely that restricted common connections can be found between otherwise distant sets. Note how the blue set connects the green & orange sets that are some distance apart.