After Effect: How do I achieve the smoke effect?
It's difficult to tell from your question exactly what you're trying to do.  If you could link to a video of the effect you're trying to reproduce, or phrase your question more specifically, you will get more helpful information.

If you're looking for realistic smoke, fluid dynamics simulation isn't really something that After Effects can do on its own.  You'll need to get the physics right in another package, and probably render it elsewhere too, then maybe composite it in After Effects.  This is an extremely complicated topic, and there isn't one tutorial that covers it all.  But you might want to look into some other software like this.    

But if you just want to "fake" it, you can just use different layers of fractal noise attached to particles.  For this type of effect, search videocopilot.net for tutorials on  Red Giant's Trapcode Particular.