Sandworms are very large and dangerous creatures, and you could get youself killed if you tried to ride one without the proper instructions.
Now you might be thinking to yourself, "When am I EVER going to use this information?!" But you WILL be thanking me one day, when you are stuck on the desert planet Arrakis, with NO means of transport, just roasting away in the hot sun.
Now the most important thing to remember is that you MUST have the right equipment.
1. Maker Hooks
You will need these to mount the sandworm. Without them you have no hope of controling the beast.
2. Stillsuit
Now what self-respecting desert traveller walks around the desert without his stillsuit? You MUST wear your stillsuit at all times in the desert!
3. Thumper
The thumper is a mechanical device used to summon a sandworm. You will need this if you want to summon a sandworm and hope NOT to be eaten by it.
So, now that you know what you need to carry, let's move on to the method.
First, you must make sure that your stillsuit is fastened properly. You don't want to be running alongside the sandworm and trip over yourself just because you never bothered to learn how to tie your boots up now do you? You will want to put those nose plugs in as well. (Not only is it good for keeping sand out of your nose, but those sandworms REEK of spice.)
Next, set the thumper, and activate it. Then find a tall dune to stand upon, so that you may watch the arrival of the sandworm. It's not fun to have a 300 meter (or longer) monster sneak up on you, and it's even less fun to have the 300 meter monster swallow you whole.
Sandworms summoned by a thumper almost always make their presence known, you can see them moving just under the surface of the sand, which allows you to gauge the size of the worm. This is important because for every meter of the sandworm's diameter, you must a half a meter away. This distance is required to avoid being sucked into the vortex of it's passage, but still have the time to run upto it and mount it.
Once the sandworm is close enough to mount, run alongside it, and throw your maker hooks into its sides. You will want to aim for the ring segments on the sandworm's surface, if you miss, the maker hooks won't hold on to anything.. and you will probably get crushed under the rushing sandworm. When your hooks find their mark, pull yourself onto the worm, making sure that you keep the ring segment open. Failure to do this cause the sandworm to roll over, and YOU WILL GET CRUSHED! (and then everyone will blame me for not explaining the dangers of having a gigantic worm SQUISH YOU!)
If you followed all the instructions properly, you should be on top of the sandworm at this point. It cannot roll over and crush you as long as you have those ring segments opened up. The sand irritates the soft fleshy insides of the sandworm, and it will to it's best to keep any exposed portions as far away from the ground as possible. This knowledge is useful, because now you know how to steer the darn thing! Using the maker hooks to open ring segments on the sandworms sides will force the worm to turn in that direction.
A few points one must keep in mind when riding a sandworm:
1. No shields.
Never ever wear a defensive shield in the desert. You might as well take off your stillsuit and pour ketchup on yourself if you wear a shield in the desert. Shields attract sandworms and cause them to go into a feeding frenzy. It is the equivalent of blood in shark infested waters. I personally would want to avoid being ripped to shreds by multiple sandworms.
2. All equipment is in working order.
Even though you have all your equipment, you'll want to make sure that they are all in working order. Make sure the hooks are still in working condition and the cables are not frayed. Many young Fremen have died because of frayed cables. Frayed cables are NOT funny. Stillsuits have to be properly fastened, lest you waste your own moisture. And for GOD'S sake, make SURE that the on/off switch on the thumper works properly. You do NOT want that thing to suddenly start thumping while you are still checking the rest of your equipment.
3. Do not be cocky
The number one cause of accidental sandworm riding deaths is not being able to handle a sandworm properly. The number three cause is frayed cables on the maker hooks. Frayed cables are NOT funny. The number two cause for accidental death is when a young fremen thinks he has control of his sandworm, (get your mind out of the gutter, I was talking about the makers of spice on Arrakis... erm, you know what I mean!) he starts grandstanding, doing stupid things like saying "Look ma! No hands!" at which point the maker hooks slip out of the ring segments, and the sandworm decides to roll over, crushing it's poor rider. And THAT, is always funny.
So there you go! You've just learned how to ride a sandworm! Just remember, there are no brakes on these things, so when you want to get off, there's no point looking for a parking space. Just make sure that you leave the sandworm someplace where it can just quietly and peacefully slide away into the desert.