With regards to hiding, make a macro to hide.. then just walk around (or stay still) with the button held down.
To gain stealth (after hiding is 50), use a moongate as it will automatically hide you. Jump the gate and take a step.. repeat.
All skills have ~8 seconds of delay between uses.
Hiding requirements have been reduced to 30, you only have to have 30 hiding to start training stealth.
One method of gaining is with ninjitsu and meditation, but thats for people with higher hiding who are training stealth. Just make a macro to walk in one direction towards a blocking point ( cliff, tombstone, tree, etc... ), add shadow jump to macro and last target ( where you will jump to ). When the macro is run you will walk into your chosen blocking point, cast shadow jump, be teleported a few steps away, and you will stealth back to blocking point. Like I said, good for people who already have hiding, but now want to add stealth and ninjitsu.
Another method is very similar, and is perfect for newbies. It requires a customizable house! Place teleport tiles on each end of a room, making sure the one you're walking to is against the wall to stop you from walking past the tile. The teleporter will relocate you causing you to walk against the wall towards the other one again, an endless walking path. Macro only needs to contain walking in chosen direction and hide skill. This option is best for newbie because when in a house you own or are friended to, you have a 100% chance to hide, no matter hiding skill level, so you will gain hiding and stealth MUCH faster.
Also, when gaining stealth, you will need to increase the difficulty to continue gaining at certain points. Ther eis a chart on-line giving optimal suggested points, but I can roughly tell you that when you reach 50 - 60 skill, you should start adding pieces of heavier armor to your suit. Start with a suit of "20 str required", then as your gains slow, replace one piece with studded armor or something that is about "35 str required" when you are finally waering a full suit of studded armor ( at about 75 skill ), you should add a close helmet to continue gaining.
Most people suggest gaining to 75.0 skill and locking it, I suggest going to 80.0, because one skill you may like is 'shadow strike', it comes as a special move on some weapons ( dagger and club come to mind ) and using it will allow you to break line of sight with whatever is attacking you and will instantly hide you and take you out of combat mode ( to stop auto defend from revealing you again ). This skill is very handy, but requires that you have high weapon skill to be able to hit something to hide, its like having smoke bombs.
If you find that you're unable to hit whatever it is that is attacking you, whack a nearby sheep or lesser animal to trigger shadow strike! Wear high poison resist! If you're poisoned and stealthing, the more damage the poison does to you, the better its chance to reveal you.