Define contact.... If you mean radio then no hurry because we have enough problems of our own to solve. But if you mean a visitation then I sincerely doubt that anyone that advanced would need to resort to violent colonization... And if they did take that route we would be well and truly screwed...

Sensible scientist fear over reaction by
the public. I heard a quote by Stephen Hawkings -"we mistreat other species here
on earth now; this doesn't bode well for
interaction with alien life" ... yet if we
present some of our humanitarian goals;
possibly strike an accord of helpful interaction. In a cards on the table/ thier
perception of us might be off kilter -as we seem to have many wars going on simultaneously (20).Have they monitored
our radio/t.v.; the race to harness energy; grow food?We would have to react on the fly
and remain flexable❇

If they come here, they would observe us from a safe distance, and say "look, the apemen have developed air travel" - then move on. I think it would be like Star Trek - observe but don't interfere.

If they contact us first it will mean they are far in advance of us. I think all we can do is ask them if they can help us not be idiots please.

My guess is advanced alien civilizations are aware of our existence, but we are still so primitive as to not be worth their time. If we assume that aliens won't come a'conquering/destroying for our natural resources (as about 95% of sci-fi films portray them), what do we bring to the table? We can barely get away from our own solar system. I think the only thing of value we might bring is our creativity in music and other art forms. That may be uniquely human and possibly of value. (Except for Close Encounters, of course. I'm sure everyone remembers the five tones. LOL!)

probably in fear & panic.

with the utmost respect and humility......but I doubt the nations will ever agree on anything - even a simple hello

Ask them to help us translate that book they left us

So many variables that it is hard to know. We will know the correct approach after we mess up the first one.

Through maths. It's about the only culturally non-specific medium I can think of.

First thing? Quarantine. We don't know what germs they have and vice versa (presumably). Second, communication. That is key. No violent show of force. No threats. But, of course, that will never happen if the US military is involved.

Say Hi and Welcome. Offer them a joint.

Reality.... military will attack.