The very first step is to make sure your fabric is on the straight grain. To do that just snip into the fabric and tear across the width. If pleating a insert to be smocked, you will tear a strip several inches wider than you need. You will be using the full 45" width of the fabric. Take the fabric strip to your ironing board and press. If the fabric is very sheer or flimsy, you can lightly starch it.
Using a wooden dowel, roll the fabric strip onto the dowel, keeping all torn edges stacked together.
Note: Different pleaters pleat fabric differently. You will notice this if you flatten out all the pleats once the fabric is pleated. One side of the fabric should have longer stitches than the other. On my Sally Stanley, I pleat with right side of my fabric up, because the long stitches will then be on the back. Other pleater models might cause you to have to pleat with the wrong side of the fabric up, therefore, it is important to take note of which way your pleater pleats, whether the long stitches are on the back or front of your fabric. Before you begin smocking, always remember "long is wrong". In other words, you want the long stitches to be on the back of your smocked piece.
Slowly, begin turning the hand crank on the right side of the pleater.
NOTE: Some people like to pleat with their pleaters turned the opposite way that I have mine and they pleat left-handed. I prefer to have my pleater needles facing me as I pleat.
I keep my eye on the edge of that fabric as it goes thru the pleater, which keeps it going thru perfectly straight.
As the pleats load up on the needles, you can begin pulling the fabric off the needles and onto the pleating threads.
Another little trick I have when pleating is that I use my left hand to keep the fabric taut as it goes thru the pleater. If you don't have it taut, you will end up with puckers and everything will get catty-wampus between the rows of pleats.
Once the piece is pleated, pull the end of the fabric off the needles. Make sure you watch all those threads so that none of them come up short and get lost in the fabric. If that happens, check out this tutorial for a quick fix!
Group pleating threads into 2's or 3's and knot them together on both sides of the pleated piece of fabric. You are now ready to block the pleated fabric and make any markings that are needed for construction.
Here is a video tutorial of mine, that gives more in-depth detail of pleating.