I've been reading the postings on tenure (and now promotion to full
professor) with interest.  Having lived at a small liberal arts
college (Hamilton College), a research-oriented university
(Rochester), and a major research university (Berkeley), I can say
one thing definitively: things vary tremendously from place to place.
There are no rules, save that there are.  What follows are some
ramblings that may or may not be useful - they sum up how I feel
about things.

When I got my Ph.D. (back when some of you were either in knee pants
or a gleam in your parents' eyes), the job market in mathematics was
taking a nosedive.  Four of the seven people who finished with me at
Stanford that year didn't have jobs by the end of the academic year.
That led to my first piece of advice, given to beginning graduate
students. I believe it to this day: Don't embark on an academic
career (be it your Ph.D. or an academic job) unless you are willing
to go through all the work, have the decision turn out negative (no
job after the  Ph.D., or a negative tenure case), and still be able
to say "It was worth it anyway."  That is: you have to love what
you're doing.  If you don't, then it's just a job, and you can get a
lot more money elsewhere.  (As a friend of mine once said, where else
can you get underpaid to work eighty to a hundred hours a week at
something you love?)

Second, harness your passion.  If you love to teach, do it with all
your heart.  If you love your research, pursue what you care about
with boundless energy.  (And if you love both, do both - that's one
way you can put in 80-100 hour work weeks.  By the way,  I'm a dad,
spend a lot of time with my daughter, love to read, and am a real
"foodie."  You can be an academic and a human being too. It just
takes discipline.)  It's the intrinsic rewards of the work that make
it worthwhile.  Interestingly enough, the people who do what they do
out of passion also do it better.

So: don't do what you need to do to get tenure.  That is, don't
slavishly follow other people's advice about the "right" things to
do.  If you do, you'll be a slave to other people's opinions and
directives for n years, after which you'll be so well trained that
you won't know what it means to follow your own star.  If you do what
you love (strategically), then you'll do it better, and tenure and
promotion will be byproducts of a happy overworked life.

Third, be strategic.  (Here my comments overlap with others'.)  Know
what the rules of the game are at your institution, and make sure you
meet the criteria.  If you love to do research and teaching is what
counts (or vice-versa),  be prepared for trouble or for a move.  If
you know there are expected numbers or kinds of publications, or
signs of high quality teaching, do what's necessary.

Make connections, both because they'll help you do things better and
because those connections will pay off.  If you're interested in
teaching, pursue information and groups that focus on doing the best
possible job in the classroom.  If you're passionate about some area
of research, send your papers to the top researchers, seeking their
opinion.  It'll improve your work, and get you into the grapevine.
(A personal story^Ê when I was starting out in problem solving, I
didn't know any better; I sent my first paper to Polya with a note
saying how I was inspired by him, and to the top tier researchers
asking for feedback.  Almost all of them, including Polya, wrote
back.  Most were remarkably gracious, something that is still true in
large measure - the folks at the top are often among the nicest! And,
my attempt to push and refine my ideas wound up getting me enmeshed
in the right community, which no doubt advanced my career, though
that wasn't my intention when I wrote those folks.)

As has been suggested, document everything.  At Berkeley we have to
submit annual "bio-bibliography" forms listing everything we've done.
I have an electronic version of the biobib form on my computer
desktop.  Any time I do anything that belongs on the record - serve
on a search or other committee, invent and teach a new course, give
guest lectures in colleagues' classes, get a grant, have a paper
accepted,  give a talk at a meeting you name it - I note it on the
form.  Then, in June, when my colleagues are going crazy filling out
this year's form (just what did I do?") all I have to do is hit
"print."

Don't be shy.  At most colleges and universities, when you come up
for promotion or tenure, you have to write a personal statement.  At
some institutions the personal statement is read directly by the
decision-makers, who may or may not know the candidate well.   For
big promotions at our place, the personal statement goes to the
personnel committee, which then makes a recommendation (via a written
report) to the higher-ups.  I can't tell you how many times I've read
personal statements that didn't represent the candidate nearly as
well as he or she could've been represented!  At times, I've made a
much better case for the candidate than he or she did.  Simply put,
not making the best case for yourself is potential academic suicide -
you can't trust that others will see the forest for the trees, and/or
make the case for you.  Nobody knows your work, how it fits together,
your sense of vision, better than you do. Explain it! Be humble if
you must, but be clear and let the readers draw their own glowing
conclusions.