You are going to use:
wool and lining in the amount needed for your height
leather or pleather for the collar (OT cloaks)
black thread
pins
hand sewing needles
really sharp scissors
white marking pencil (for the leather)
tailor's chalk or tailor's pencil
sharp leather sewing needle
heavy polyester or heavy nylon upholstery thread
measuring tape
bandaids

How much material you need depends on two things - the width of the material available, and your height in armour. Generally, someone 6' in height should be able to make a cloak using approximately 6m of 60" wide material. If your material is 45" wide, you will need about 8m of material. This is being rather generous with fabric. Remember it is better to err on the side of more, not less. You can always shorten, but adding length can be tricky if not impossible.

A quick rule of thumb is to measure the distance from the back of your neck to the floor when you are wearing your Vader boots, add 12" to that and multiply that total by three. The extra length is to allow for the neck opening and the hem. It is far better to err on the side of too much material than not enough.

Each time I make a cloak, the 'pattern' is slightly different because it has to be adjusted depending on the person's height. There are two cutting patterns to choose from, and both are easily adjusted for whatever length is needed. A trick for marking the bottom cutting line is to use a cloth tape measure pinned at the top of the triangle's point to trace out an arc on the material. You will need to cut the same number and size of triangles in both the wool and the lining, but it is possible to use a narrower fabric in the lining if you match it up with the fullness of the wool.

Note: To produce a 3/4 circle (270 degree) cloak from 60" wide material, you will cut 6 triangles. For 45" material, you will need 8 triangles to produce the same amount of fullness.

Take your stack of fabric and separate the triangles. You need to sew the long sides together, building a 1/2 or 3/4 circle as you go. Rather than fight with large amounts of material, it’s easier to start with what will be your center back seam and add pieces to each side. There is less material to manuever through the sewing machine this way. Pin and sew from the top point of the triangles towards the hem. If your materials have a tendency to fray, zig-zag stitch the cut edges before sewing the seams. Press the seams open as you sew them because it will be easier to do that at this point in assembling the cloak. Do not sew the lining to the wool yet! You just want to assemble the triangles at this point. Your assembled wool and lining in terms of layout for a 3/4 circle cloak will look like the diagram to the left.

Note: Your fabric may have slight difference from one side to the other. Make sure you keep track of which sides match and pin/sew together accordingly!

Next step is to cut the neck arc in the wool. A trick I have used is to take paper, make a pattern which fits across the nape of the neck and shoulders with that and then cut the fabric using the paper pattern. Only remove a small amount of material at a time until it fits comfortably. Alternatively, you can cut the neck as a small arc, with a diameter of ~4" and adjust from that by trimming excess material. Stay stitch (zig-zag) along the cut edge of the wool.

Hang up the wool and lining for a few days before you go to hem it. This allows the fabric to relax and stretch under its own weight.

To hem, put on your shoulder armour and Vader boots. Make sure that the wool is sitting on your chest armour the way it will be when you are wearing the costume. You will need someone to help cut away the excess material (if you haven’t already done so) and mark with pins where the cloak touches the floor or at whatever length you want it to be. Pin the wool outer part of the cloak first. This may take some time, so try not to move. Adjust the pins until you are happy with the length. Sew this hem in place, but leave the first 6" on either side of the front unstitched.

Match the lining to the wool at the top. Adjust until both the wool and the lining lay flat. This requires laying both out on the floor or other large flat area. Pin the lining to the wool at the neck and cut the lining to match the neck arc. Sew the lining to the wool along the front. Press that seam, and then sew the wool and lining together at the neck opening. The lining will hang below the wool, but don't worry about this.

Put your chest armour and Vader boots on. The lining will hang below the wool, so it is a good idea to stand on something which raises your boots off the floor a few inches. The lining should be pinned so that it will hand 1" above the wool after the hem is sewn in place. Make sure that the lining is laying flat under the wool as you pin it. Static is not your friend as it can affect how the lining drapes. Once you are happy with where the lining hem is marked, sew it in place, finishing the wool hem which was left unsewn at the front at the same time.

The neck is reinforced with an approximately 1 1/2" wide strip of leather (OT) or fabricl (ROTS) cut to match and sit overtop of the wool. Your cloak chain will attach underneath this. I use lobster claw jewelry clasps hidden under the front edge of the collar to do this. There are several ways to finish the neck. The collar can be sewn right over the cloak, or the leather can wrap over the cut edge of the neck to help protect that from wear. The inside of the collar area should be faced with the same material as the lining, cut in the shape of the collar, to protect the stitches holding the collar in place and protect the cut edge of the neck. The collar itself can be left open so that the chain can be run through it..

Vader cloaks are HEAVY. With time, if a cloak is hung up in a closet, the weight can pull the seam stitching apart. The ideal way to store a wool cloak is laid flat, away from direct light, and where moths can't get at it, but with some air flow rather than completely sealed. If a cloak gets wet, don't hang it up to dry! The extra weight from the water can pull the seams and distort its shape. Drape it over a bunch of chairs and spread it out as much as possible to allow air flow. Wool is a dry clean only fabric, but with proper care, a cloak can last for many years before it begins to show signs of wear.