"Dark Magician" monsters have several features in common:
The armor of most "Dark Magician" monsters is a collection of shiny, curved plates with sharp edges, all of the same color, which covers the torso and shoulder areas. On the edges of the plates are curved trimmings of contrasting shade.
Some of these monsters also have hats which appear to be similar to a stereotypical wizard's hat, which is usually crooked, leaning forward at the tip and with several rings which segment it. These rings are of the same color of the curved trimmings seen elsewhere on its attire.
Some of these monsters have Spell Counters embedded in their staff, shield, sword or armor.
Some also have the Arcana Seal depicted in the background.
The monsters of this archetype are fairly strong on their own, however, they rely a lot on a large amount of support cards to keep them going. The later releases revolve around spell counters. Depending on the way the Deck is built, this archetype can be very slow or fast archetype, occasionally able to out-trump even the "Blackwings", or the "Six Samurai" depending on the draw and how often "Dark Magician" can be Special Summoned. "Magical Dimension" is a great card in order to rush your "Dark Magician" out fast. Protecting a "Skilled Dark Magician" as he gathers up his counters is another way to go, but this strategy relies on how many spell cards you can allow your opponent to play before they gain the upper hand.
Magical Dimension- Arguably the best way to special summon a spell caster. As long as you have a spell caster on the field and one in the hand, you can get out your Dark Magician and even destroy one of your opponents monsters. Additionally, this is a quick play spell and therefore can be used quite flexibly throughout the duel.
Ancient Rules- Hate drawing into Dark Magician? He can be pretty useless in your hand unless you have an Ancient Rules to instantly special summon him.
Dark Magic Curtain- Dark Magic Curtain's high cost can be curtailed with Spell Economics, however the summon restriction and the fact that Dark Magician must be in the deck for you to activate it makes it a card worth running only one copy of in your DM deck. Use it in conjunction with the Thousand Knives and/or Dark Magic Attack in your hand before your opponent can destroy your magician.
Sage's Stone- It is highly recommended to run Dark Magician girl in a DM deck, so that you can use Sage's stone to quickly get out your Dark Magician.
Magician's Circle- Useful to quickly search out a Dark Magician Girl from deck to use that Sage's Stone in your hand. However, searching out a Gagaga Magician for a convenient Xyz summon can be just what you need in certain situations.
Swing of Memories- Quickly bring a normal monster (DM) from your graveyard until the end phase. Good if you have a DMA or Thousand Knives in your hand as well as a DM in the grave. Very situational and can be a dead draw.
Dark Magic Attack- Clear out your opponents back row if you have dark magician on your side of the field. Can be a game changing card against S/T heavy decks, but can be sided out against deck that do not use many S/T's.
Thousand Knives- If DM is on your side of the field, destroy one monster your opponent controls.
Bound Wand- This is a great way to protect your Dark Magician once he gets out onto the field, since he is not the easiest monster to get out there and you want to keep him in play as much as possible. Also, this card brings him up to an impressive 3200 attack points.
Escape from the Dark Dimension- A great side card for a Dark Magician deck, for decks that like to banish your ace card.
Gagaga Shield- Throw down your Dark Magician in defence mode and equip him with Gagaga Shield if you need to play defensive for awhile. This way your life points will be safe and you can immeadiately make use of any Thousand Knives and Dark Magic Attack that you draw.
Skilled Dark Magician- This monster needs 3 spell counters to bring out a DM from the hand deck or graveyard. Also a nice 1900 beater!
Dark Effigy/Double Coston- Both of these cards can be used to tribute summon DM, if you are not able to special summon him.
This archetype also lacks support, with only "The Eye of Timaeus" supporting the archetype as a whole. Most support for cards in the archetype is for "Dark Magician" himself or Spellcasters in general.