With only Origins cards facing only Origins cards.
Limit the deck to 60 cards. 23 lands, 37 non lands. Of those 37 non lands, use about 20 creatures and 17 non creature spells.
Of those 37 non lands, stack them by their converted mana cost. Your goal point is an average converted mana cost of 2.5. Starting out, use either a monocolored deck or two colors. The allied pairs, those touching on the color wheel on the back of the card, are easier to pair than the opposed.
Once you've met the above, look at the cards you've chosen versus what remains. Is there a coherent theme: fast creatures and damage to the face, control with a few trump cards, beat sticks waiting on mana ramp, etc? Keep you're average mana cost down.