Carnival makes the tipping easy - they automatically will charge your onboard account $10 per person/per day, which will cover your cabin and dining staffs. You can adjust this up or down by going to the guest relations desk. They work hard to earn this and many people end up either increasing the amount by going to the guest relations desk or by just giving some extra cash to the workers in envelopes. All drinks purchased at bars automatically have 15% added for tips.
Expect beer to range from $3.25 to $4.50 or so, depending on brand. Carnival also has Foster's oil cans which are a good deal at $5.75. You can also save a couple bucks by getting a bucket of beer, which is four beers in a bucket of ice. Mixed drinks are around $4.25 to $7.50. Again, 15% is added to these prices.
Security is quite noticeable in some ports, less so in others, but that doesn't mean it isn't there. You need to have ID and your cruise card to leave and re-board the ship. The ship will have a photo of each passenger that appears at the security check point when you scan your cruise card. They take the photo on embarkation day. The ship will x-ray all packages and bags entering the ship, and you will have to go through a metal detector. The same holds true on embarkation day - the terminal security is much like that at an airport.