Since now is one of the best times in an expac to learn how to improve ones knowledge of a class, in preparation of a new tier, I wrote up a simcraft guide for one of my guilds. It is here. Please provide any feedback, if anything is unclear, and most importantly if anything is incorrect.
Hope this helps.
Simcraft is an amazing tool in the arsenal of the serious raider. The ability to derive accurate stat weights for a variety of fight types and lengths, and then utilize those weights to perfect your character is of great benefit. However, a caveat. As with any tool, the usefulness is limited by user knowledge and problems which exist inside the tool itself. This guide is an effort to aid in the learning of how to get stat weights and use a tool such as AskMrRobot to min/max. As it is a first draft, errors in the guide may exist, and I would appreciate any being pointed out so I can correct them.
As well, note that errors in Sim-c individual class/spec modules *may* exist. This will depend on how well your class can be modeled, and how good those who edit the modules are at what they do. For example, the fury module is amazing. The DW one is incredibly solid, but Unholy, due to the nature of the spec isn't quite as accurate for true DPS results, but is solid on stat weights. Likewise there is currently a "feature" on AskMrRobot where Amp trinket weights are being increased even on custom weights, while Sim-C has already done so, effectively double dipping. Be aware if anything incredibly odd seems to be going on. It may be a bug.
On to the fun stuff! First step is to make sure you have the latest version of Simcraft. Download it here. http://simulationcraft.org/ After doing that, unzip it and open the application named SimulationCraft.
Head over to the Import tab, and find your character.
Make sure everything is right for the fight type you want to simulate. Check glyphs/talents/gear/trinkets, etc. Now click "Import!"
This page is the meat and potatoes of Simcraft. It's the operations list for actions. Although these can be edited to test different things out, Simcraft can be buggy if you don't phrase things correctly. Basically, don't change anything here unless you know what you're doing. Look but don't touch!
Next step is to setup the parameters for your specific sim. To do that click on the tab "Options". Those options with arrows are the most important to adjust. Generally 10k iterations is enough, fight length should be adjusted to mirror length of typical fights, as should be fight type. Personally I use 450 seconds near the start of a tier, which is 7.5 minutes, and 300 seconds near the end, which is 6 minutes. Fight types I generally juggle between patchwerk and light movement for the classes I play. If you hold your curser over the fight style drop down menu, it will describe what each type of fight changes. You can also add threads if you have a PC which can handle it to increase speed.
These options will give you average DPS over 10k iterations for that fight length and style. There is one extra step for stat weights. (I'm assuming all buffs/debuffs will be present in 25m. Those can be changed in buffs/debuffs tab)
For weights head over to "Scaling". Shown is an example of what I sim for a duel wielding strength class. You can run all, but it takes much longer and most of those numbers aren't relevant.
And that is it! Hit "Simulate" in the bottom right, and wait! You'll get a page such as this once finished.
Normalized numbers are simple normalized numbers where your primary stat is always 1. Those are useful for determining upgrades in your head through napkin math. (In the case of higher item level but worse itemized loot. Is it an upgrade? You can use those numbers to determine the "value" of each piece to decide)
Once you get those numbers take a look at the "Scale factor" numbers. Those are what we want. Head over to http://www.askmrrobot.com/wow/gear. Import your character. Hit "Edit Weights". Type in the results from your Scale Factor page. Hit "Save". Hit "Optimize." Fix anything that is off that *Does not look sketchy*. AMR is wonky at times.
UNEQUIP THOK'S TAIL TIP BEFORE OPTIMIZING.
AMR is increasing the value of mastery by the amplification amount if it sees you have on a Tail Tip, so if you have on a tail tip it's increasing the value by an extra ~7-9% ABOVE what it should be, which will skew results. Same for haste, although that really shouldn't impact much if anything.
And there you go!