After playing Eve for seven months I have finally figured out how to stack weapons.
The tutorial doesn't tell you and most pvp guides don't tell you but it's a very significant boost to your damage in all forms of Eve combat.
A new player will have a frigate with up to 4 weapons on it. To activate those weapons he or she will press F1, F2, F3, F4.
A veteran player will drag those weapons all onto one button. To activate them he or she will press F1.
That gets your weapons active a lot quicker than the first method plus it's more relaxed.
To set this up you will need to discover the little white Options arrow to the bottom right of the round ship monitor in the middle of the bottom of your screen.
Right click it to open it up. Two options need to be set: Unlock Modules And Enter Grouping Mode. Next make sure you're not currently using the modules you want to move, they need to be inactive. Unload them (you can do this by right clicking them and choosing Unload to Cargo. Then simply drag all the weapons on top of each other.
My Drake has 7 missile launchers grouped on F1. I've just discovered this and I really like the new playstyle that finding this has given me.