Alta is also known as "the Aurora Borealis city".
Alta Airport is the busiest airport in Finnmark. Widerøe  provides services from regional destinations including Kirkenes and Hammerfest while Scandinavian Airlines  and Norwegian  has depatures from Oslo and Tromsø.
The tourist information seems to move around on a daily basis, so the first thing you might do is wind up traveling all over Alta looking for it. As of 29/06/2012, the information center is in the Nordly hotel, on the left, just as you enter town from the South. (You may notice other information signs as you travel through Alta, but almost all of them point to centers that have closed.)