How to combine different projects to create final clip in After Effects? I am new to video editing and learning Adobe After Effects CS6. I have downloaded different templates from the web and edited them and now I want to create a final movie by combining all the clips.

Some clips/projects have different resolutions - I have rendered all the projects separately and created individual .mov clips.

Now I want to create final movie by combining all the clips.
First, you don't want to render the clips prior to final output if you want maximum quality.  You instead want to use nested compositions.  Really, final assembly is ideally done using an actual non-linear editor, such as Premiere, however you can accomplish the same thing by putting together a composition and using each of the compositions you have made as assets.  Then, when you output the final render, it will render what it needs from each of the nested compositions and keep the highest possible quality.

Note that you should use nested compositions regardless of if you use Premiere or After Effects.  Premiere will import compositions directly from After Effects if you import the After Effects project in Premiere.  You may also have to apply scaling in order to get the clips to match resolution.