Here is another tutorial, covering basics in Creating an object and a tile. Nothing fancy, but some general tips/tricks and cheats, that I find useful when working on things in Max. These should apply to Gmax or 3dsMax as both offer the same sorts of options.
Creating Objects/TilesThe above does NOT cover adding a tile to a tileset or any of that sort of thing, nor is the result from the tutorial anything really useful, but the tips can help anyone aspiring to start a little further along the learning curve of creating custom content for NWN.