If you are new to the game and plan to place bets on it at an online casino, then you should really try to practice craps first so that you know how to play online craps properly and know what to expect and what to do when you are faced with the real thing. You may find that there are many players around the table who are more experienced than you, and this can make you feel quite pressured; while you can alleviate this by finding a "private" style game in which you do not see others around the table, you will still need to act, and taking the wrong strategy when you are playing for money could have catastrophic effects.
Even when you know the rules of craps, that does not necessarily mean that you know how to play it. You should practice craps betting strategies so that you can figure out what is best for you and which types of play you prefer to use. This will help you to feel more comfortable in the game, as well as allowing you to move forward a lot faster when you are playing against others in a real online money game. While the board and the dice may be virtual, there is certainly nothing virtual about the money that you will lose, so practicing your game is a good way to eliminate any stupid mistakes and make sure that you fully understand the odds!
You can find plenty of places to practice for free, especially on the internet. Since you are going to be playing online afterwards anyway, it is a great idea to learn how to play through this medium so that there is no confusion when you eventually start to play for real money in online casinos. You can easily find a site providing free games just by doing a simple search of "free online craps" or a similar term, and you will find many results to choose from. You can try a few different ones to see which has the best graphics, allows you to play with the biggest amount of credits, or so forth, depending on what your tastes are, so you can use this to help you decide which place to play at for practice and also what kind of place you should be looking for when you start to play for real. You may also be lucky enough to live near to a land based casino that offers a free "training" area where you can learn how to play the games, but these are few and far between so the internet is probably your best option.
Remember to keep in mind all of the strategies and the craps tips that you have managed to pick up while you practice craps, as this should help you to come up with the best game play and allow you to make the most of your time practicing. Try out different bets and see what the outcome will be, and above all enjoy yourself!