One thing about the .40 S&W is the pressure is warm and the case is small, so it's easy for something like seating a little deep to screw you up by raising pressure. So, watch that your bullet seating depth is no greater than was used by whatever source of load data you used.
Seating Depth = case length + bullet length - COL
Start with a small load and work up toward the maximum while watching for pressure signs. I maintain a list of pressure signs, here
. Richard Lee's rule of thumb to from the starting load to the final load in five steps seems to work well for handgun loads that start 10% below maximum.
For the shooting itself, if the handgun is one I've never fired or sighted in before, I'll check sights on a 25 foot target. I'll continue at 25 feet with a 2" or shorter gun, but move to 50 feet for two and a half and 3 inch guns, and the rest get 25 yards.
I use a large white posterboard with a piece of typing paper taped or stapled over the center. I aim by centering the front sight post to have equal size strips of white on either side of it and half the height of the page above it. This is partly a psychological ploy in that it avoids you worrying about score. At first, all you should worry about is group size. That blank page seems to absolve one of any temptation to "ambush the ten ring" by yanking on the trigger, too.
Start with the light loads. I shoot 10 to get a group that has better statistical significance, but have used five if the gun tended to give me touching holes, and six with a revolver. Label the center page with the load and replace it and go up to the next load up.
After you've got all 50 rounds down range (assuming you didn't have to stop because of pressure signs) see which group is smallest among the loads that functioned the gun properly (we hope they all did). Go with that one. Take the best measure you can of the group center location for that target and use that for fine sight adjustment. If you take a picture of the target center or scan it later, you can use the free On Target software
to help you with that. Just use a ruler to add a point right at the center of the page to identify the center of aim, which the program will ask you to pick. Also, draw a measured 6" line through it so the program's measured length calibration feature can be applied.
The program will give you the location of your group center as well as its size. With those two pieces of information you can select the best load (if it wasn't obvious) and fine tune the sights.