There are many other rules in ITD&TD, each mentioned in their own section, however, there are some additional rules that should be gone over here, to help understand all other rules.
Sometimes, you will need to do some division. If you do so, and end up with a fraction, you round down, even if the result is one-half or greater.
Lots of rules are presented in this book. However, some rules break generalized rules in some way. If a specific rule contradicts a general rule, the specific rule wins.
Although you may only play with 4-6 people at a time, the game is meant for large groups to all be playing in the same world, though not necessarily at the same time. The passage of time should be tracked. Characters should age, and years should go by during campaigns.
A good rule of thumb is that for every 1 day in real life that you don't play, 1 day in game-time happens. Characters should be investing in "downtime activities" for these periods of no adventuring. GMs and players should work out what happens during these times before or after a session, or even between sessions. These should be well recorded for other players to get a sense of what's going on (unless it should be a secret!).
Sometimes, you may need time to speed up or slow down. For example, adventuring in the winter may simply be too dangerous, and all players agree that they would rather wait for late winter or early spring to start up again. Go ahead and simply roll the calendar forward several months. If players had particular goals during this time, you could always handle them on the side. Alternatively, you may slow the campaign, or halt "in-game" time completely for some outside situations.
Regardless, it should be well communicated with all players.
It has never been easier to keep in contact with groups of people. I recommend a Discord Server made specifically for tracking your game, although email groups, Facebook groups, google groups, slack, and a vast amount of other products can help communicate with each other.
However, a GM may ask you not to use devices at the table, unless it is clear that you are using it to play the game. This should be figured out in Session 0, but some GMs prefer paper character sheets with physical dice, and others are okay with digital character sheets.
Please be respectful of each other as you play. Some topics which may be okay for you may not be for others. Hash out what is and isn't acceptable before you play (Session 0 is the best place!) and remember that there is no wrong way to play, but there are vast enough differences where people may simply not agree to play well together.
Make sure to discuss how to handle player-vs-player at your table before play starts. Specifically in session 0. Many tables have different ways of handling it. Some allow it, others don’t. Some have a hybrid system, and some only allow it when it makes sense.
I recommend that player-vs-player content simply not be allowed at your table.
But if you feel that player-vs-player content should be allowed, I recommend using the following rules: If player-vs-player comes up, the “target” of the action simply gets to chose the outcome. If a player thief is attempting to steal from them, the victim gets to decide if the attempt was successful, if it failed, or leave it to the dice if they wish. This allows players not interested in player-vs-player to have a kind of “opt-out” function, and allows players who want to engage the ability to “opt-in”.