Venice is a fantastic place for a short break so you're bound to have agreat time.
If you're arriving into Marco Polo airport (not all cheap airlines do!) transfers couldn't be easier.
there's a waterbus runs between the airport, the Lido and main island and it's well signposted in the airport or you could just follow the crowds.
If you really want to push the boat out and arrive in style you could leave the crowds and get a private water taxi (they go from the same jetty). It's a fantastic way to arrive (a bit James Bondish skimming over the water in highly polished wood speedboat).
But be warned, it doesn't come cheap, last time I was there it was about 70€ and that was a couple of years ago!!!!!