Most attacks follow the general attack rules, except as indicated below.
General Attack Rules
When you use an attack, you declare which attack you are using and pick its target or targets, then roll the d20 for each one to find out if you hit. The attack will indicate what happens to a target that you hit (and sometimes one that you miss).
Ranged Attacks
Any ranged attack (weapon, spell, power, ability, or whatever) draws opportunity attacks from enemies engaged with you that you don’t target with the attack.
Spell Attacks
Most spells draw opportunity attacks from enemies engaged with you, even the enemies you target with the spell. Close-quarters spells are the exception; they don’t draw opportunity attacks.
Like weapon attacks, you add your level to the attack roll for spell attacks, plus any magical implement or other bonuses you might have.
Target Hit Points
Some spells and effects target creatures with a certain number of hit points or less. The hit point value you use is based on current hit points, not starting hit points.
Crits
Every attack roll that is natural 20 is a crit (“critical hit”) for double damage.
Crit Effects
Standard crits deal double damage and, at the GM’s discretion, might entail some additional superior result.
If you manage to double your crit damage (through the effect of a talent, power, spell or other source), triple it instead. If you manage to double your triple damage, bump it up to quadruple, and so on.
Crit Range
Crit range is what you must roll to score a crit. The standard crit range is a natural 20. Some powers and spells expand your crit range. Each point of improvement drops the number needed to score a critical hit by 1.
Fumbles
Rolling a natural 1 has no effect on the target, not even miss damage. At the GM’s discretion, rolling a 1 while in a precarious position might entail a bad result for the attacker. You might also hit an ally if you’re shooting into melee.
Damage on Miss
By default, a miss deals no damage, though some attacks are an exception. These attacks specify what happens on a miss.
Flexible Attacks
Flexible attacks allow you choose your target first, make your attack roll, and then use the natural unmodified die result to determine which of your eligible flexible attacks to use. You still use the modified roll to determine whether or not you hit, but your flexible attacks trigger off the natural result on the die sitting in front of you.
You can only use one flexible attack at a time.
You can’t use a flexible attack when you make an opportunity attack.
If you have some attacks that are flexible and some that are not, declare whether you are making a flexible attack or a specific non-flexible attack before you roll.
Unarmed Attacks
To punch or kick, make a Strength attack with a –2 penalty (regardless of your class) against AC. If you hit, you deal 1d6 damage for every two levels you have, plus your Strength modifier. At odd levels, including 1st level, use a d3. If you miss, no damage.
Two-Weapon Fighting
You fight as normal, generally using the weapon in your main hand to attack. If your attack roll is a natural 2, you can reroll the attack but must use the reroll.
You do not get an extra attack for fighting with two weapons.
Some classes (and class talents) provide other advantages when fighting with two weapons. Those classes still get to use this basic two-weapon advantage.