help with git usage

I've been trying to use git for awhile now, (and I've read a lot of documentation, though maybe my comprehension has not been high enough) but there are several operations which I can't figure out:

1) After cloning a repository from work at home, making some changes  
and committing them,
I use "git push" to push them back to the work repository.  The  
changes seem to make it to the
work repository (I see the commit message in git log), but I can't  
figure out how to get the
changes into the working set at work.  (evidently not merge, checkout  
or reset -- seems like it
should be merge, but)

2) I can't figure out how to get back the latest (or any other)  
version of a file I've modified (or deleted)
in the working set.  (Well, I suppose I could checkout the whole tree  
somewhere else and copy the
relevant file, but I'm hoping there's something simpler).

3) Similarly, I can't use the little context diffs I can see in git- 
gui  -- I need to see side by side comparisons;
I've become accustomed to tkdiff.  It seems like git mergetool knows  
how to do that in some restricted
circumstances, but I want to do it outside the context of a merge.

Thanks, -- danq