I am writing this because I think the Rulebook falls very short and right now the forum/wiki/community just isn’t distilling things easily for people. (This is definitely stuff for a wiki of sorts).
To WoTC, you can improve the status quo! It will help ensure that new purchasers, that purchase out of curiosity, get hooked and stick with you on this new and novel endeavor. The fans probably love solving the puzzles of unclear things... I’d even dare say the Rulebook needs a 2.0 printing. You could start with updating the official "FAQ" page...
The following is roughly organized, but it is only trying to be a direct, clear and concise gathering of things you need to know that the rulebook didn't emphasize well, or omitted. Furthermore, this is stuff you read after reading the rulebook, not instead of!
I would be delighted to edit this post in order to correct it, improve it, etc. So if you have any comment, please do offer it up! I am missing a fair amount of "where this comes from" which I'll try and add in soon.
Movement, and Squares
- A legal square is a square that isn't more than 50% covered (black, or otherwise out of the play area lacking grid lines)
- All movement, special or normal, must end in a legal square; for example, phasing and burrowing cannot end in a wall square even if it went through them.
- Any effect that asks you to move N squares really means “move up to N squares”.
- You may not move diagonally around the corner of a dungeon tile wall corner; you need to take two steps to walk around it. This restriction on diagonal movement does not apply to outdoor tiles.
- Phasing and burrowing allow you to ignore walls during your movement (thus you do not apply any wall corner restriction). Flying does not ignore walls.
Playing your Order Cards
- When a card or other action says it taps the creature, you tap the creature first and then play your action
- Playing Standard and Immediate cards require you to tap the creature before playing the card
- Minors do not require an untapped creature; they do not tap the creature
- Creature attacks (melee, ranged) are Standard actions
- Only Immediate cards may be played in response to other cards; stated in terms of the Stack, playing Standard and Minor cards may only be played against an empty stack (community.wizards.com/go/thread/view/758...)
- Immediate cards may be played anytime
- Standard and Minor cards may only be played on your turn, during a creature’s activation, and only by the active creature
Melee and Ranged Attacks
- Melee across the diagonal corner of a wall is OK (community.wizards.com/go/thread/view/758... )
- Dodging can only be used against ranged attacks, not melee (source: see above)
- Ranged when adjacent to an enemy is not allowed; this means you may not do any ranged attack, whether the adjacent enemy is the target or not
- If a card says to "make an attack" and has a symbol then a "+nn", it means you add nn to the standard attack printed on the creature's card corresponding to the symbol (melee or ranged). If +nn is missing, this is the same as +0.
- The Cleric may heal upon deployment; the arrow icon is intended to be the Immediate icon
- Named Powers do not stack (“Block 10”, etc.)
- Damage from terrain, “end of activation” triggers go on the stack; may be responded to
- Even cowering cannot prevent damage labeled “cannot be prevented” (community.wizards.com/go/thread/view/758... )