Note: There are over 40 pages of Indoor Soccer Strategy, Drills, Tips and Tactics on SoccerHelp Premium.
A few ideas:
BEST TIP: The best outdoor goalie may not be the best indoor goalie. An indoor goalie doesn't need a strong leg; the most important quality is quick hands. Your goalie is HUGELY important in indoor. I suggest putting the player with the quickest or second quickest hands in goal, even if it is one of your top field players. A way to test this is to stand about 5 steps away and throw the ball at them. You will soon be able to tell whose reflexes are best. However, I wouldn't make anyone play goal who doesn't want to. If you have an active goalie, let her come out with the attack if you are safely ahead or behind. It is surprisingly hard to score even if the goalie is out of the goal.
2ND BEST TIP: Stress one-touch shots and try to get your quickest scorer in scoring position as much as possible to be ready for rebounds (quickness to rebounds to get off a one-touch shot is very important). This means the player who has the quickest first step, best anticipation and who is aggressive.
Rules vary by tournament; we don't believe there are any standard rules. Contact the organizer of the tournaments you plan to participate in and ask them to fax or e-mail you the rules several weeks in advance.
You will have to decide how much you want to stick with your regular style of outdoor play versus playing the ball off the walls.
I found it helpful to get there a few hours early to watch the tactics used by the other teams. We played a lot of games in gyms, with different sized playing areas and conditions, and getting there early allowed me to see what the conditions were.
Keep in mind that, to a degree, indoor usually equalizes the speed factor because the fields are small. This might help you or hurt you.
If you only play 5 + the Goalie, think about having a roving "Center" player who plays both ways (i.e., comes up on the attack but drops back to help defend). We played 5 + Goalie and I found this a good approach. This player will get tired and need to be subbed.
Like in outdoor soccer, when your goal is under attack you probably need to leave a Forward/Midfielder out at the halfway line to win cleared balls.
If you play 2 Forward/Midfielders, think about having them play close together so they can work together and try to be sure one of them is a good dribbler who can penetrate to pull the defenders.
If the indoor goals where you play are small, it will mean that most of the goals will be scored from close range (because the goals are so small). If this is the case and your team is really good, you should control the ball and make a lot of short passes to work it into scoring position. Otherwise, your best bet is to try to get your Forwards in front of the goal and then send the ball into scoring position as much as possible (tell your other players to pass to space near the goal front, not to feet, and to rebound the ball off the walls if that is allowed).
Try these games in practice, they will help: "Dribble Across A Square, Premium Version", "2 Team Keep Away, Premium version" (which involves many quick transitions from offense to defense), "Small Sided Scrimmage Without A Goalie" (which forces everyone to learn to defend and to work the ball close to the goal before shooting), and other similar 4 Star Games such as "Attack & Defend Ball Tag". These can all be practiced indoors.
We suggest just having fun with Indoor Soccer. It is very different from outdoor soccer. Also, if you play on hardwood floors, encourage knee and elbow pads. We found they helped.
Use "painter's tape" to mark "goals" (or targets) on the walls, and for lines or marks on the floor (if you need to). It is easy to remove and doesn't leave glue. You can get it at Home Depot or Lowe's in a bright blue color.
Make your goals small and if you scrimmage, don't use a Goalie (play the "Small-Sided Scrimmage Without A Goalie" game from SoccerHelp Premium). This will force your players to learn to quickly transition and that every player must play defense when your team loses the ball, and that they must try to use their foot or body to block shots.
Play the "2 Team Keep Away" game on SoccerHelp Premium. It teaches quick transitions and is very fast, as is indoor soccer.
I tried the fluffy "indoor" balls and the small "futsal" type ball (a small ball with little bounce), but ended up just using regular outdoor balls, because I felt it was more important for every player to have a ball to practice with. I suggest taking a little air out of the balls to slow them down and so they have less bounce. Some coaches use a smaller than normal ball, but there might be disadvantages to this, since it will play differently from a normal sized ball.
If your objective is to prepare for outdoor, I suggest not playing off the walls -- keep it as realistic to outdoor as possible.