The Parachute Adams certainly needs no introduction but tying it in sizes smaller than an 18 can get a little tricky. Hopefully some of the following tips will help to ease the pain.
Here, I'm going to tie one on a size 22 TMC 100 dry fly hook. Make sure you mash the barb before you begin tying as small hooks like this can be difficult to remove.
For small flies like this one, I really like Danville's Flymaster 6/0. Here I'm using Olive. Start your thread about halfway down the hook shank and take wraps rearward to just above the point.
I got the following tailing technique from watching a Charlie Craven video and it's one of the best I've ever seen. From the outside edge of a brown hackle neck, select a relatively web-free feather with straight, stiff fibers. Pull the fibers down until they're perpendicular to the stem and then strip off 5 or 6, keeping the tips aligned. Place them on top of the hook shank, there's no need to measure yet, and secure them with a single turn of tying thread. This is really just a convenient place to hold the fibers.
Now, select an equal number of fibers from a similar grizzly hackle and strip them from the stem, once again, keeping the tips aligned. Align the tips of the grizzly hackle with the tips of the brown hackle and get hold of them with your left hand. Unwind the single thread turn and pass the fibers to your right hand. Measure the fibers to form a tail about a hook shank in length and then, using a pinch wrap, secure them to the top of the hook shank. Take wraps rearward to above the barb then forward to about halfway up the shank. Pull the fibers back and snip them off close. You can then advance your thread to cover the butts.
For the wing post I like white polypropylene yarn. Snip off a segment about a card's width in length. Separate the strand into 2 equal parts and then separate one of those parts in half again, so you're left with a 1/4 strand of yarn. Fold the strand around your tying thread and pull it up to vertical. At this point adjust the post location to get it to about the 3/4's mark on the hook shank. Take a wrap in front, one behind and then a few more in front to secure the yarn.
Quality hackle is absolutely key to this pattern and I've found none better than a Whiting saddle in midge sizes. This half saddle is a Furnace, while this whole saddle is a Grizzly. Even though all the feathers look really small, you still need to accurately measure them to get just the right size. This grizzly is a true 22. Select and measure a brown or furnace hackle as well. The closer the two hackles are in size, the better.
Lay one of the feathers on top of the other. Although order doesn't matter, make sure both shiny sides are facing toward you. Pull down and strip about 1/8th of an inch of fibers from both stems. Tie the bare stems in just behind the eye and take wraps rearward to the base of the polypropylene.
Now comes the fun part. Place just the smallest drop of Zap-a-Gap on a sticky pad. With your bodkin, pick up just a bit of the adhesive and apply it to the base of the wing post. Lift both hackles along with the yarn to the vertical position and give them a twist, which will cause the Zap-a-Gap to set. If you're unsure that the set is complete, just give them another little twist.
What this procedure does is stiffen and stabilize the yarn as well as adhere the bare hackle stems to it. This makes the whole process of posting the wing with your tying thread much easier. End with your tying thread on the far side of the hook, just behind the wing.
For small dry flies like this, I really like Super Fine dubbing. Here I'm using Adam's Gray. Pull only the smallest amount from the packet. It's very easy to over-dub flies this small. Make a short, very thin dubbing noodle on your tying thread and, starting at the base of the tail, dub a tapered body both fore and aft of the wing. End with your tying thread immediately in front of the wing on the near side of the hook.
Pull the hackle fibers down to perpendicular, the dull sides of the feathers should now be facing up. Begin making clockwise wraps around the wing post, 2 to 3 turns ought to do it. Bring your tying thread to horizontal and take 2 wraps between the body of the fly and the hackle while pulling the remainder of the hackle down. Then pull the post back to expose the eye and take 2 good firm wraps behind the eye to anchor the thread.
You can then do a 3 or 4 turn whip finish. Pull the thread nice and tight and snip or cut it off close. Even if you catch a hackle fiber or two, the eye should still be clear enough to easily tie on the fly.
With everything properly secured, reach in with fine tipped scissors and snip the remainder of the hackle off close. Finally, trim the wing so it's about a hook shank in length.
It's surprising how visible this teeny post is on the water. Despite it's diminutive size, a Parachute Adams tied on a 22 floats remarkably well and just seems to catch fish when nothing else will.