The Base

Make your shield using at least one layer of core fluting, which you can purchase from Bunnings, among other places.  I recommend using either three layers of core fluting, or two layers of core fluting and one layer of floor matting.  Cut your sheets of core fluting/foam to roughly 60cm.  If you don't have a jigsaw (even an old school one), and couldn't be bothered getting one, then read ahead first to double check measurements.
http://i184.photobucket.com/albums/x27/Soulsmith_1/Shield%20tutorial/1_zps575dee13.jpg
Once cut to shape, glue your sheets together using contact cement.  I use Kwik Grip Advanced, though a lot of foamsmiths use Sika.  If you use more than one layer of core fluting, make sure the direction of the fluting runs in different directions when glued together.

Once your core fluting/foam layers have thoroughly dried from gluing, you can cut them to the exact size.  Assuming you plan to make a 60cm diameter shield, cut your sheets to a diameter of 56-57cm to allow for the foam padding on the edges.
http://i184.photobucket.com/albums/x27/Soulsmith_1/Shield%20tutorial/20140623_140515_zps6ae332fd.jpg
I own an electric jigsaw, so this job is easy for me.  If you don't have a jigsaw, then you're probably better off cutting your disks to the exact diameter before gluing them together.

Once your glued disks are cut to size, tape them together around the edge.  This not only helps hold the disks together, but reduces damage to the interior of the foam padding later on.
http://i184.photobucket.com/albums/x27/Soulsmith_1/Shield%20tutorial/2_zps2c868eb5.jpg
At this point you have a solid shield-like disk.  If you plan to make arm straps for your shield, cut lines in your disk to feed your arm straps through.

The Boss
(skip this section if you only plan to have arm straps for your shield)

This section deals with including a punch grip and shield boss.
The punch grip handle itself is cut from the shield base, then reinforced.  Start off by cutting out two half circles as shown below.
https://i184.photobucket.com/albums/x27/Soulsmith_1/Shield%20tutorial/3_zps89443fc9.jpg
I measured 3.5cm between the two 'D' cutouts.
https://i184.photobucket.com/albums/x27/Soulsmith_1/Shield%20tutorial/4_zpsc463d90f.jpg
I cut these shapes out with an electric jigsaw, but you can easily do it with an old steak knife (I've done that too)
https://i184.photobucket.com/albums/x27/Soulsmith_1/Shield%20tutorial/11_zpsd6c588ad.jpg

Next up, cut two strips of core fluting the same width as your handle, and a few inches longer than the handle.  Make sure to cut the strip in the same direction as the core fluting runs (you'll get what I mean when you go to cut it out).
https://i184.photobucket.com/albums/x27/Soulsmith_1/Shield%20tutorial/5_zps71923d6a.jpg
In the above pic I pre-taped the handle before attaching the re-enforcing strips of core fluting.  You can do that, but you don't have to.  I did that for extra strength on the handle.
Tape your re-enforcement strips to the handle, making sure there is equal overlap at top and bottom, and then tape the overlap down too.

Next up, tape and wrap your handle.  I use bicycle inner-tubing cut into long strips, then wrapped around the handle like tennis racket tape, but you can get away with simple cloth or electrical tape.
https://i184.photobucket.com/albums/x27/Soulsmith_1/Shield%20tutorial/6_zpse3e82b04.jpg

Next up, the boss.
There are no pics of me taping the foam padding to the boss.  Why?  Because it's a plastic cereal bowl with foam padding taped to it.... *shrug*
Just make sure you get a bowl that will give your knuckles enough clearance when you're holding the handle, especially seeing as you'll want to pad the inside of the bowl with foam as well as the outside.
https://i184.photobucket.com/albums/x27/Soulsmith_1/Shield%20tutorial/7_zpseb509555.jpg
Also don't forget, no metal bowls for your shield boss.  Why?  Because it's in the rules that you can't use metal.  I know it'd be stronger and less likely to shatter, but it'd also be more likely to accidentally hurt others during unintentional shield bashes.  Just pad your bowl like crazy to reduce the chance of cracking it.... and buy spare bowls.

Tape your bowl to the front of your shield.
Tip:  Only use two pieces of tape, then triple check it's on straight, and that it's comfortable to hold from the inside.  Then tape the boss down securely.
https://i184.photobucket.com/albums/x27/Soulsmith_1/Shield%20tutorial/8_zps5c4ca39a.jpg

The Padding

Keep in mind, rules say your shield has to have a minimum of 1cm of padding on the front.  If your shield base has a foam layer (like the top left in this pic) then that's fine.  If your shield's face is core fluting (like the bottom shield in this pic) then you'll need to add foam padding.
http://i184.photobucket.com/albums/x27/Soulsmith_1/Shield%20tutorial/9_zps3c296f7a.jpg
If your shield only has arm straps and a flat face, you can cut out a circle of foam and simply stick it on.  If you have a punch grip shield with a padded boss, you can do what I did and cut out two donut shaped disks of foam, tape them together, then tape them onto the shield face (as pictured top right).

Next up, the edge.
https://i184.photobucket.com/albums/x27/Soulsmith_1/Shield%20tutorial/10_zpsae82a74e.jpg
Pretty self explanatory.  Get a couple lengths of piping insulation foam (the same kinda stuff you use to make spars), split them down the entire length on one side, and stick them around the edge of the shield as shown.

Make sure to tape down your foam padding around the entire edge of the shield, especially if you plan to use the shield as it without a cloth cover.  Taping the foam down protects it from damage when it gets struck.  Just make sure you tape the foam down lightly;  no need to compress the foam at all.
If you decide to make a cloth cover for your shield, you only need to tape the foam padding down around the edge enough to make sure it's secure and won't come off.

The cloth cover itself will protect the foam from most damage, although as with any jugger equipment, occasional repairs will be inevitable.
https://i184.photobucket.com/albums/x27/Soulsmith_1/Shield%20tutorial/12_zpse04521df.jpg
How do you make a cloth cover?  Well, the basics are;  cut out a circle of cloth at least 40cm larger in diameter than your shield.  Next up, either tape it down onto your shield (as pictured above on the left), or get heaps fancy and sew a drawstring into the cover.  How to do that is for another day :-)