Cruise planning may not be rocket science but it can be complicated. One of the more difficult factors to nail down is when to book your cruise. Should you book a year in advance to lock in just what you want, or hold off as long as possible in order to get the best price?

There is probably no single best answer, given the variety of cruises, changes in company policy and marketing practices, political events and other factors. But there are some guidelines that can be helpful.

First, you should definitely shop around. No two cruises offered are exactly alike, but there are so many good cruise lines today that you can get an excellent voyage on several different ones. Also, since the Internet has made researching them not only infinitely easier but even fun, you’ll find more choices than you could possibly investigate.

After you’ve done some initial research to get the range of prices for the season and destination of your choice, you can start to zero in.

If you have to take your vacation on specific dates, you are limiting your choices. Just as with the airlines, if you are flexible on your departure/return dates you will be on track to getting a better price. If you’re locked in for whatever reason, be sure to book as early as possible – preferably at least six months in advance.

You won’t usually be able to take advantage of the absolute best possible price by booking early. Some companies are not accommodating when it comes to changing dates, though you may be able to get an upgrade to your cabin. But you will have a nearly-guaranteed reservation. No company can fully guarantee any specific departure date or cabin, though most have an excellent record.

Being flexible allows you to take advantage of the deals that do pop up from time to time. You may be able to book a superior cabin on a stellar voyage with little notice that way. But you need to be prepared to act quickly. That means you need to have a passport and other documentation already in hand and be ready to leave home on short notice.

Naturally, if your destination is less popular or if you choose to go during the off-season, you’ll have more options. You’ll have a better chance to get a great price for a good cabin.

The Alaska season, for example, runs from May through September. That isn’t just because people prefer to travel during summer months. Alaska can become horrendously difficult to travel to during the winter. Modern technology hasn’t completely conquered the weather, yet.

As a result, peak sailing dates between July and August sell out around 9 months in advance. Booking for early in May will give you more choices, but keep in mind that the weather that early can be challenging in some years.