This is how I made my Bo Shuriken, it took me a while to figure it out and hopefully my instructable will help you as well.

Step 1: Materials

You wil need:
1) A drill
2) A bench sander
3) Some 150 grit sandpaper (or higher for a more polished look)
4) A steel rod of your choice (I used 3/8 inch but you can use 1/4inch or any other you prefer) found at the hardware store
5) A ruler (or any other accurate measuring device)
6) Parachute cord (optional).

Step 2: Measuring and Cutting

How long do I make my Bo Shuriken?
This is entirely up to you, however, some sizes like 50 ft may be impractical... By general rule of thumb: 8 inches if you have small hands, 10 inches if you have average hands, and 12 inches if you have really big hands.
To cut, simply measure, mark, and cut with a dremel tool. If you don't have a dremel tool then a cut off wheel, or a fine toothed saw will do the trick.

Step 3: Cleaning It Up

If your rod is not already polished, then you can do it quick with a drill. Put the rod in the drill as you would a drill bit and run it while sliding sandpaper across the rod. Be sure to flip it around to polish the end that's in the drill.

Step 4: Get to the Point!

Ok, so some have used bench grinders to sharpen their Bo Shuriken. But I found it much easier to use a bench sander and a drill. Start by marking how long of a point you want( I chose 3/4 inches), then place the rod in the drill as before. Turn on the sander, and drill, then place the end of the rod on the belt to start making the point. Be sure to not keep the rod on the sander too long because it will get very hot. You can either sharpen the point straight or rounded( I chose rounded). If your belt sander had very rough grit, then be sure to go (carefully) over the point with the 150 grit sand paper.
Side note: Please be sure not to touch the rod until you have run water over it or let it cool down a while because it is very hot.
Another side note: this does not need to be heat treated to harden the point, after all I've put my Bo shuriken through, I've not had any problems with the point. If you make yours out of a different material then what I made mine from, you may experience a weaker point and have to heat treat the tip.

Step 5: Finished?

If you have read carefully, and not burnt your self, the congrats you should now have a Bo Shuriken.
But wait... A question mark? Is there more?
Yes, if you want to go a bit further, you can add a nice parachute cord handle. Gut the cord and tie a long two bight turks head knot near the dull end for better grip. Be sure to shrink the cord after you have tied the knot to prevent if from sliding off.
Note: my Bo shuriken turned out to be closer to 9 and 7/8 inches, or to be more precise, 24.95 cm. ( pun not intended)

Step 6: Wait! How Do I Throw?

Explaining how to throw with words is complicated, so I suggest you look up videos of people throwing it and watch how they stand, how they hold the Bo shuriken, how they move their wrist, their release time per distance, ect.
To hold it look at the picture above, and when throwing you release with the thumb.

Step 7: Safety

I must start by saying I'm not responsible for what YOU do with your Bo Shuriken. Use at your own risk and PLEASE DO NOT THROW AT PEOPLE OR PETS*. Alwase watch your surroundings for people and pets so you don't accidentally hurt someone.
Store your Bo Shuriken in a safe place where no children can get ahold of them and/ or play with them.
In the case that your Bo Shuriken may ricochet or bounce back I recemend you not try to catch it.
* unless your being attacked by a life threatening person or pet.
I hope you all have enjoyed my instructable, let me know your thoughts and opinions in comments.
Happy throwing!