What supplements/aids have you found most useful for DMing D&D, both at the table and in prep?
Prep:
- graph paper, coloured pens/pencils, various other drawing and drafting supplies
- adventure modules of all kinds - even if I'll never run it as is, any module - no matter how bad - can still be mined for maps or ideas or whatever
- hard copies of any books or other materials I need
- pre-printed forms (character sheets, xp and finances tracking sheets, etc.) in quantity - if players use a standardized character sheet, finding info on it is much easier for you-as-DM
- coffee
- time
At the table:
- a big-ass table - no table is too big
- a handy place to store what I'll need, be it shelves behind me, a small table beside me, a box on the floor, or (like me) all of these
- DM screen with all my notes/charts/maps/tables paper-clipped to my side of it
- chalkboard, chalk, eraser (for drawing out maps of what they see)
- minis in vast quantity - no matter how many you have you'll all too often find you don't have the one you need - and of course dice
- a pointer (low tech: long stick; high tech: laser pointer) for indicating something on the board/map you can't reach from behind the screen
- in case questions arise, some version of an Arms and Equipment Guide and a Castle-Builders Guide are often useful
- note paper - large, for you to make your game notes; and small, for you to send hidden info to a player when required
- beer
Lan-"by no means is this a full or comprehensive list"-efan