Ok here are 10 rules for making the perfect Deathmatch level(s):

1-> Light levels should be kept at extremes. Either extremely low
    or extremely high or it has a blinking behavior. Have a good
    mix of the three. Small areas should have low light levels or
    blink and large areas have high light levels{or vice versa}.
    
2-> Levels should be decorated with items such as torches, symbols etc.. 
    Try to make it detailed as a house. Remeber the object appearence  
    viewing limit of 64{or somewhere close to it}!  
    
3-> Barrels should appear quite often in your level{Remember: they
    don't regenerate!!!}. Don't group more than 4 or 5 together.
    Don't have more than about 2 groups per room: 1 group for small
    rooms and 5 or 6 for very large fields etc... balance it out.

4-> Have small amounts of monsters or none at all. Monsters that drop
    ammo{like heavyweapon dudes and shotgun guys) are to be left
    able to travel outside a cage. Monsters that don't and shoot 
    fireballs or other projectiles should be kept in cages.(I mean
    literally). Monsters that must be close up to attack(such as lost 
    souls, demons and specters etc..) should never be in a deathmatch 
    level. Always play with respawn on if you have monsters to keep
    the action going{the shotgun guys effectively give an unlimited
    supply of shotguns and heavy weapon dudes give you an unlimited
    supply of chainguns}. Never use lost souls or pain elementals in
    a deathmatch level...

5-> For weapons there are two rules: there should be either equal 
    amounts of each and the more powerful weapons harder to get or
    more risky to get or more the weaker the weapon the more often
    it appears. One rule applies to both, however:weapons of high power 
    should be spread out or there will be only one part of your level 
    in which action is going on. THERE SHOULD BE AT LEAST ONE OF EVERY
    WEAPON ON EACH LEVEL.

6-> The wall textures are up to you but have a good variety as with
    the floor and ceiling textures. Have certain rooms with certain 
    themes. For instance, don't put a twitching body in a restaurant!
    It would be a good idea to put health bonuses in a bar, thought
    because it simulates the drinks that are available.

7-> Have a good number of the following: Acid pits(or lava, slime etc..)
    so players can fall into or be blown into; Crushing ceilings both
    slow and fast; windows so people can sniper from; ledges for people 
    to sniper from; moats; lifts; assault towers; teleporters etc... 
    A warning: don't put to many moats, pits and crushing ceilings! 
    But use windows, sniper spots, ledges, assault towers, lifts
    and teleporters as often as you can but don't over do the lifts
    and teleporters! 
    
    PLEASE NOTE: Refrain from using switches that do permanent alternations 
                 to your level! 

9-> Make sure your level is a little small. For a good deathmatch level,
    design it for 3 players so 2 players can have a little hunt and
    4 players can have a Fragfest...

8-> Using the modified wad_auth.txt, here are the extra things I put in:
    No. Of players: This suggest how many players would fit 
    this level for deathmatch. Place a number 2-4. 
    Monster Types: Place the types of monsters that are in your level. 
    Story: Place the story of you wad here.
    
9-> Spread out your items. Don't group items next to each other or
    it will allow a player to "hole up" and become impossible to defeat.
    Don't place to much cell ammo or a player with a plasma rifle or bfg
    will become impossible to defeat. Never place enough ammo for a bfg
    for more than 1 or 2 shots or your deathmatch level will be ruined!!! 
    (but you can always take some cells away...) Invisibility and 
    invulnerability spheres don't regenerate for deathmatch 2.0!!!!

10-> Try to rid your level of the HOM effects and imperfections. If your
     entire level is perfect except for one room, fix it!!!]

     
      That's about it. I wrote this text file because too many people are     
      making bad deathmatch levels these days(sigh) and I hate it...
      
      P.S -Make sure your level comes with a demo displaying all 
           the secrets of your level!!!
          -Refrain from using co-op exits in your level!!!
          -ALWAYS DESIGN YOUR LEVELS FOR DEATHMATCH V2.0!!!
           Who plays 1.0 anyway?!

      Arachnotron(or Pagemaster whatever)