The Cons of 'S'

When animating in Maya, there are several ways to create keys. I think the most easiest way is to press 'S' key.  But the big problem when using 'S' key is, it creates its own tangent which may ruin the timing and the spacing of the animation. Although I don't care how the graphs look like, these uninvited tangents make me annoying to spend extra time to fix it because it actually affects the animation somehow, especially in polishing stage.

Thanking to Michael Comet, at least I don't need to fix those tangent each by each, Using autoTangent.mel can save huge amount of time. But this is not a fundamental solution to prevent it. 

So what I simply did is using this command, 

setKeyframe -insert;

This makes that I can put new keys to all current attributes which have keys already, without affecting any other tangents. This is pretty much same with the second button(insert key) of the graph editor. (It's also same with pressing 'I' + MMB)

The only difference with that is, the button only works on the selected curve but the command works to all keyable attributes whether selected or not.

Now I have the original 'S' key mapped in 'Alt+S', which previously used as ToggleFBIKEffectorsPinState (which I don't know what that command is), put the command I show to 'S'.

And for 'Alt+S', I add a command at the end of the line

//this is the original command of 'S'

performSetKeyframeArgList 1 {"0", "animationList"};

//these are what I added

evalEcho "timeSliderSetTangent step";
timeSliderSetTangent step;

Because I will use 'alt + S' when blocking stage, the last two commands make the curves stepped key.

Now I have three different methods to key.

Alt+S : create key to all keyable attributes with stepped key. 

S : insert key to ALL keyable attributes without affecting tangents.

I+MMB : insert key ONLY to selected curve without affecting tangents too.

The first one is for blocking, the other two for the in-progress stage. Really handy!