Tipping is optional and typically given the last evening of the cruise. You can sail with anywhere from 100 passengers to almost 3,000. Experience atmospheres from casual to formal, classically simple to ultra deluxe. Sometimes space is available due to cancellations. But to get exactly the ship, cabin and sailing date you wish, book early.
Most cruise lines offer early booking discounts for customers who plan ahead.
Remember also that last minute air fare can be very expensive. The money you might save on last minutes cruise space can easily be offset by high air rates. For Europe, South America, Asia, Africa, Russia, Scandinavia - Yes, and sometimes a visa is also needed. In Mexico and the Caribbean, US citizens need a certified copy of your birth certificate with photo identification or a valid passport. Check with you cruise consultant for documentation requirements at your destination.