How do you attack in dungeons and dragons?

Answer 1

It depends on the edition. Since I doubt it is first or second we can ignore the ThAC0 system... I'm going to go over 3.5e since it is the one I'm most familiar with.

Melee attack:

You take your to hit bonus (determined by class), strength bonus (not strength amount but strength bonus), and any other misc modifier. These could include class specials or a weapon being +x (where x is the total you add to your to hit). Masterwork weapons also add a +1 to hit, but this is not stackable with a magic weapon's bonus (i.e. a +1 dagger has a +1 to hit even though it is also masterwork). You then roll a d20, add the to hit bonus, and that's your total attack. If it equals or surpasses your opponent's armor class then you hit.

For damage you add your strength bonus and other misc modifiers. Masterwork weapons do -not- add to damage, but a +x weapon adds x to the damage. Then you roll the weapon's damage and add the bonuses. Some magic weapons will allow you to do special damage, such as adding another 1d6 of fire damage, which is all added into the equation. If a monster is resistant to a specific kind of damage than you have to make sure all types of damage are kept track of separately (because the monster could resist some of the damage but not other parts).

Ranged attack:

Add to hit bonus, dexterity bonus, and any other misc modifier. Roll the die, add the total, and it again has to equal or surpass the opponent's armor class.

For damage you roll the weapon's damage plus misc modifiers. If it is a strength bow (I think called great bow, but not sure. Look at the bow's description) you can add your strength bonus up to the bow's amount.

Thrown weapons:

These ones are a bit more odd. A thrown weapon uses ranged weapon rules for the to hit, but melee weapon rules for damage.

You also need to be familiar with critical fumbles and hits. A critical fumble happens when you roll a natural 1, while critical hit happens on a natural 20. A natural roll means whatever the die rolled without any bonuses, sometimes also called "nat". A nat 1 is an automatic miss while a nat 20 is an automatic hit. There are more rules with critical hits that are beyond the scope of this question, but you need to be sure you understand critical hits.