Time remapping ,how?

I have a question how to make time remapping ,for example:
I have animation ,in some moments action is to slow or to fast or even not that it cult be (yeah i can make that perfect for the beginning but that aren’t so simple ), differences in tempo aren’t so terrible but that’s make me crazy ,when in some moments …you know .
So how can i make that with the best solution (It doesn’t matter how difficult that cut be ,it must work)
Sry for my english .
Edit ,i mean animation with armature .

its what theNLA <link>is for.

And another question ,when I have just one action ,and it have all the movements rotations and another things ,can I still use NLA to time remapping? (Resulting from idea of NLA i must have more than one Action) And when not ,how with this one action make few actions ,for example :
Walk Cycle ,jump etc ?
Sory for noob questions ,i can rigging and animating but I still can’t understand this all NLA ,action etc. When you have just pencil and white paper that all stuff is unnecessary ,and now I will go into higher level ,so i will to understand how its work ,anyway thanks for help.