In order to start building you're going to need something more than a creative world and a vanilla client. While there are a few options to go with, your best bet is a Bukkit server with world edit. A basic guide to downloading and running Bukkit can be found here. This may sound daunting, but if you're only going to be using this server for building maps on your own, the process is really as simple as downloading Bukkit and running it. Once it's run once and created the rest of the files, download WorldEdit from here and place it in the plugins folder. Then run it for real, and connect to it from Minecraft with the address “localhost” (127.0.0.1).

Once you're ready to start building, familiarize yourself with these common WorldEdit tools:

• Selection Commands (Start Here)
  • Click for a basic guide on how to select a region.
• //farwand
  • Turns the tool in your hand into a WorldEdit wand with unlimited range.
• //set [block]
  • Turns the entire selected region into your block of choice.
• //replace {block} {block}
  • Replaces one block with another in a selection, or if only one block is given replaces all non-air blocks in the selection with that block.
• //copy
  • Copies the selection to the clipboard, with your relative position as its anchor. (Click here for a guide on clipboards and anchor positions).
• //cut
  • Copies the selection but also removes it.
• //paste
  • Pastes the clipboard relative to your current position as if it was the anchor position of the clipboard.

• //stack {number} {direction}
  • takes your selection and pastes it [number] times (once by default) right next to your selection in the given direction or the direction you are currently facing by default.
• "-a"
  • Flag that can be added to paste and stack that makes it so that air blocks in the clipboard/selection do not overwrite non-air blocks when they are pasted (IE: “//paste -a”).
• //rotate [degrees (90, 180, 270)]
  • Rotates your clipboard clockwise around its anchor position.
• //flip {-p}
  • Flips your clipboard in the direction you are facing around its center, or around your anchor position with -p.
• //brush [shape (sphere, cyl, clipboard {-a})] [block] [radius]
  • Turns your held tool into a brush that will paint wherever you point and right click (Click here for full brush documentation).
• //mask [block,block...]
  • While holding a brush, sets a mask of any specified block(s) that from then on that brush will only replace those blocks.
• //smooth (applies to selection) or //brush smooth
  • When used on terrain, will attempt to smooth its slope (VoxelSniper is a much better option for heavy terraforming).
• %block,%block...
  • For set, replace, and brush, you can define your block as a random selection of multiple blocks separated with commas.

Optional Plugins/Tools:
VoxelSniper – An alternative to WorldEdit that allows for much better control over terrain and terraforming.
NBTEditor – Allows you to define custom items, mobs, and spawners ingame.
WorldEditCUI – Clientside mod that displays your WorldEdit selection as a wireframe.

Once your map is built according to your sketches, you have a chance to make large changes that won't interfere with aesthetics. You'll likely want to make some now that you can look at your design in three dimensions, so don't skip over this step. Start looking at expected player flow (and in the case of a competitive map, theorycraft positioning), and make adjustments to the dimensions of just about every part of the map until you're satisfied. Examine line of sight from as many angles as possible, and remember that sometimes the strongest cover comes in the form of larger map geometry. Finally, tweak chokepoints and individual pieces of cover as needed.

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