I DO NOT RECOMMEND REMOVAL OF THE THROTTLE BODY TO CLEAN IT, EVER. Especially if you have a DBW (Drive By Wire) throttle. People come to me all the time saying that they've done this and an almost equal number report problems worse than what they had before the cleaning. Heed this warning. You don't need to remove a throttle body to clean it. If you have a DBW throttle body, DO NOT MOVE THE THROTTLE PLATE MANUALLY TO CLEAN IT, especially with the key in the ON position. This will confuse the computer and it will have to be reset in order for the engine to start and run again. In fact, this is the same thing that might happen if you remove the throttle body to clean it. Once you find yourself in this position, you're going to have to find someone with the proper scan tool to relearn your throttle position.
To avoid this, have a buddy in the vehicle with the key on. Have them depress the gas pedal all the way to open the throttle plate so you can gain access to do your cleaning. This will likely prevent you from upsetting the throttle position and causing the condition mentioned above. Honestly, the only time I recommend cleaning a throttle is when it's sticking. I've personally never seen cleaning a throttle body correct an idle issue. I think it makes you feel better more than the car. Don't get me wrong, clean parts are usually working parts, but in the case of the throttle, I only recommend cleaning the throttle body if you notice your gas pedal sticking or hanging up when you use it.
Your intake gets dirty because of one main reason: the PCV (positive crankcase ventilation) system. Actually, it's a worn engine, but the PCV system delivers the gunk from that worn engine. The PCV system helps vent crankcase pressure and reduces emissions. Whenever you have moving parts in an enclosed space, like pistons moving inside an engine block, you need to vent the pressure that inevitably builds up.
Modern engines use the PCV system. Before the PCV system, engines used an oil draft tube that vented crankcase pressure to the atmosphere. The PCV system vents crankcase pressure and fumes back into the intake manifold to be re-burned. The PCV system also uses engine vacuum to help aid in the removal of this pressure and the fumes created inside the engine. The addition of engine vacuum is what makes it a positive system instead of a passive system like on engines with oil draft tubes.
As the engine wears, cylinder wall clearances get larger, piston rings don't seal as well, and there is more blow-by during engine operation. Blow-by is the combustion gases that leak past the piston rings; it’s what is mainly responsible for the buildup of gunk in your intake. The more worn your engine, the more blow-by you have. The more blow-by you have, the more gunk buildup in the intake and throttle body assembly.
In summary, you can clean the throttle body all you like, but the fact is, if your engine is worn, your intake and throttle body will continue to get dirty. Don't remove the throttle body to clean it; you don't need to. Cleaning your throttle body likely won't do anything to solve an idle problem. It might make you feel better, but it might do little to solve an idle problem. If you have a DBW system, I would recommend leaving it alone, as you could cause more problems than you solve with a cleaning. Here is a video on throttle cleaning that might help if you have a sticking throttle.