Practice
No truer statement has been made then the old adage, "practice makes perfect". All of the additional items below provide practice but I encourage all players to play the full actual game as frequently as their schedule permits. Only by playing the game in its entirety can one fully appreciate the complexities of the game.
If you are new to the game, start off slow, use the OI starter scenarios before graduating up to the Core Rulebook scenarios and then into ITS. Only handle the rules that you are interested in and can handle. Infinity offers up a wide variety of rules, many of which are complex in nature. If you really want to use Camouflage rules but don't think you can handle hacking at the same time, then avoid taking a hacker (and definitely avoid a camo'd hacker). Limit yourself to what you need and rely on your opponents to fill in details of what they are doing. Also, ask questions. If you don't know what your opponent is doing, ASK.
Deployment Games
Deployment in Infinity is important. So many things can occur because of bad/good deployments that players really need to understand the ramifications of how they deploy their troops. Do you deploy aggressively to force AROs? Do you deploy defensively to protect your own troops? Did you cover the backfield and board edges to protect against AD troops? Do your hackers have appropriate repeater coverage across the board? Players must be able to make these decisions relatively quickly when deploying and within the context of what terrain exists on the table and whether they have first turn/first deployment/etc.
Deployment games are exactly what they sound like. They are games where players deploy their troops and then make constructive criticism of their opponents deployment. Players will decide on a mission, and play through the pregame (Initiative roll, deployment, reserve, etc). After each player deploys the opponents will gain some time to give suggestions, hints on what their plans would be if the game was played out, or other insight into how they deployed the way they did and how they would react to their opponents deployment. Change the mission and the terrain between each game.
This can be done with only a single player but that does limit the independent feedback. Still, this is a great way to practice covering fire lanes, backfield, and Anti-Impersonation attempts.
The Switcheroo
Infinity offers so make different troop types with different profiles that comprise the eight factions the numbers are mind boggling. While there is some truth to the note that many rule and equipment can be duplicated across most of the factions, each of them functions a little differently within the context of that faction. Gaining an understanding of how these small differences between factions affects their overarching strategies can be difficult, especially if the local community is small or clusters around 1 or 2 popular factions (otherwise known as the Marine Syndrome).
The switcheroo requires two players who each play different factions and swapping lists. So each player will have a viable list from an opposing army. Ideally, each player should give some insight into how these lists should operate but that isn't required. The other issue that should be addressed is that of closed information. Unlike other games, certain information is not revealed to the opponent such as AD/TO units waiting to reveal/come on board, Lieutenant status, etc. There are several was of dealing with this.
First, each player can simply agree to not use closed items in their lists and have a gentleman's agreement that lieutenants will not be targeted unless they are the only viable target. Second, players take 4 order monkeys that are identical and have a lieutenant option open to them. If the lieutenant option costs SWC, then pay the cost but the player using the army gets to decide which of the 4 models representing the base troop profiles represents the lieutenant. Lastly, leave roughly 50-60 points and 1SWC open in each list for each player to select a lieutenant and possibly some AD/TO troops.
The Proxy Game
I never considered anything like this until I started playing Infinity recently. My common foe, Tim (of Miniature Tim), has taken his time prepping his Infinity models and so, when we play, he usually uses my vast array of Infinity miniatures to proxy his Yu Jing. Now, I don't own much Yu Jing, and I won very little HI, so just about everything is something completely different. Tim will tell me at the start of the game which miniature is what and what weapon they carry, but it does tend to get a little muddled in my mind as the game goes by.
So what can a proxy game show you? Well first it requires that you remember what model represents which profile. Think of it as big adult version of the old game, "Memory" from childhood (you know, the one where you flip over cards and try to match pairs). This means you need to keep track of more things on the tabletop then just positions of the enemy, objectives, and your own forces. It really requires that you take a second to evaluate what you see because that Ghulam with the commanding view of the fire alley is really a ZuYong Invincible with an HMG.
With the proxy game you and your opponent agree to the tenants beforehand and pick a scenario and point level like usual. When putting miniatures on the field though use proxy miniatures, i.e. miniatures that aren't representative of the actual unit and profile, to represent your forces. At the beginning of the game, disclose all Open information with the opponent on what each model represents. Then play as normal. You can ask your opponent for open information at any time regarding his forces but, try to keep track in your head.
Time Trials
The basic premise behind time trials is to give yourself a limited amount of time to play or perform some sort of in-game action. Most frequently this involves playing game rounds but can just as easily be extended to deployment practice. Players can opt to work on this with friends or on their own. Decide how much time you want and what task you want to constrain via time and then get practicing.
I cannot stress how important this sort of practice is if one plans to participate in an actual ITS event. Nothing frustrates an opponent more than not being able to finish the game. At least if you make an honest attempt to play turns quickly and concisely the opponent will be less disappointed than if Captain Indecision mulls every possible outcome of every possible order.
Keep in mind that tournament rounds vary from an hour-and-a-half to two hours but that's a full 6 player turns plus pregame. Try and get Deployment down to less than 5 minutes and constrain each player turn to 15 minutes. If you are new to the game, then try for 10 minute pre-game and 20 minute player turns. The first few time trials, keep a stopwatch handy and just keep track of time. After the third time, then start implementing harsh penalties.
Don't have all your models deployed at the end of the 5-10 minute deployment? Then they don't get placed unless they have AD. Didn't use up your last 3 orders before the clock ran out on your player turn? You just lost them and it's your opponents turn now (and they should have the same restrictions). It's sad to say but this sort of learning experience goes a long way into shoring up the need and ability to play faster. Just don't let yourself become too impetuous!