Understand the costs involved. The city of Venice sets the official rates for the rides, which can run anywhere from $40 or $50 to well over $100 for a 40-minute ride. You can add more time in 20-minute increments. The price gets higher at night, and you aren't necessarily going to get the whole 40 minutes. The prices and times are not a law, but more of a guideline, and during busy times, you might not get the full time. You also will have to pay extra for things such as singing by the gondolier. Negotiating with a gondolier is common practice.
Pick a time. The middle of the day is the most popular time, so take a ride early in the morning or later in the day. Early is easiest and cheapest, but the night, of course, is more romantic.
Decide where you want to take ride. There's no bad place in Venice to take a gondola ride, but you might have a personal preference. If you want the spectacle of the Grand Canal, get on board near the Rialto Bridge or Doge's Palace. A quiet, romantic ride, on the other hand, is easier on a side canal away from the water taxis.
Book a tour through a travel agency to skip the worry about finding and haggling with a gondolier. You can pay a set price and pay in dollars rather than euros.