Reverse shaping--making the left and right sides of a vest;
or making 2 sleeves, 2 pantlegs;
or in the instance of stuffed animals and such, 2 ears, arms, legs, etc., can cause some anxiety for any stitcher.
This also holds true for items made in pairs - gloves, mittens, socks, slippers.
One solution that can often be used for both knit and crochet work is to make 2 simultaneously. In knitting, it can be easy enough to work the same pieces together on the same needle - this is particularly true for small pieces. On a doll dress, for instance, in knitting one can transfer the left sleeve stitches to a stitch holder, work across the back, transfer the right sleeve stitches to a stitch holder, work across the front, then work from left right front to left front side to side, or in the round, and take care of the sleeves last. I do this all the time. It ensures that the same amount of rows have been worked, and that the sleeves are indeed the same length. It works great for Barbie shorts/pants too. If you find you can use this method, please do. It will save some frustration.
Working two pieces at the same time can be done for crochet as well. I don't know many crocheters who don't own duplicate hooks in the same sizes. Make both pieces simultaneous, row by row, or round by round. If you don't have 2 of the same size hook, work one round, pull up a long loop as a place holder, and move to the other of the "pair" and work a round; continue alternating in that fashion. Is it more a pain to work with one hook on two pieces at the same time than use two separate hooks for each row or round? Perhaps. However, the payoff is knowing that each row or round is exactly the same as the other.
These tricks come in handy even for the most seasoned stitcher.
Lastly, another trick is to work from "both ends" of one skein at the same time. This is wonderful if you're making something small, or adding trim to a different area. I recently made a puff sleeve vest and found myself making the sleeves by working from both ends of one skein. By both ends, of course what is meant is the center pull and the outer portion of the skein...which assumes you're yarn is in skein form.
If you aren't using a skein, do yourself a favor and divide your yarn into 2 balls if you have intentions of working sleeves or similar.
That's it for now readers. Happy stitching to you all.