I'm sorry, but much of the advice you have been given so far is not particularly helpful. There is a better way to raise skill in stealth, it is done this way:

Start a Ninja character using the pre-made Ninja template. You can choose to take the starting Ninja quest or not, it is up to you, but it is not difficult and gives you some gifts that you might like. This pre-made template will start you with Hiding and Stealth higher than you would get any other way. It also gives you access to the Animal Forms Ninja spell, which gives you two animal forms (sewer rat and rabbit) that boost your Stealth by 20 points.

So: you start with 50 Hiding and 30 Stealth using the pre-made Ninja template, and can boost stealth to 50 by going Rat or Rabbit. Add two pieces of jewelry with as much stealth per piece as you can possibly find. Say that you find ring and bracelet with +15 Stealth, this will take you to 80 Stealth while in Rat or Rabbit form. Add a Burglar's Bandanna minor artifact for +10 Stealth on top of that, for 90 Stealth. There your are!

Now your task is to train up your natural stealth so as not to need these crutches. Do this (wearing just a robe) by using a combination of jewels and rat/rabbit forms that will take you to around 65-70 in Stealth, and stealth around Haven doing escort quests. Take off jewelry a piece at a time as your Stealth raises to the 75 skill level; when you have all your jewels off, switch back to Human form and put your jewels back on to go back to 65-70 again, and repeat the process.

Once you are at 80 natural Stealth skill you will never fail at Stealth when you attempt it, but it's better to take it to GM level so you don't get revealed so often. After 80 skill level you won't gain much unless you wear heavier armor. All that you need is a full suit of studded leather armor, this will take you all the way to GM. You'll fail at Stealth quite a bit for that last 20 points, but it's worth it in the end. If you can get someone to take you to the Blackrock skill gains area, it will go much faster.

You don't have to actively click the Stealth button on the Skills gump. Instead, make a macro: use skill/hiding and put it on an easy-to-hit macro (the F1-F12 function buttons are perfect for this). Then hit your macro to hide, and once hidden, start to walk slowly to begin Stealthing.

Good luck!