My cube has often been described as a constructed cube. What is meant by this is that I tend to include cards with synergy that enable other cards or strategies. The decks that people playing my cube end up building look more like archetypes you find in constructed formats past and present rather than the more conventional style of limited deck just with very high card power levels. This is a personal preference of mine having always been a constructed player and deck builder, but it does also allow for greater versatility of the cube experience.
One of the most common ways for me to cube is one verses one, each player making two decks thus giving four matches to play with their decks. There are many ways you distribute the cards, initially I enjoyed rotisserie the most, now I tend to simply make a gentlemanly agreement with my opponent where we each choose decks that don't interfere much with the others and just get on with building. Drafting is more fun when you have six or more people, with just two it is all about the construction and playing and thus being cooperative leaves more time to do the good bits!
My cube resides between 360 and 720 cards and has no balance in the colours. I find if you attempt to have an even colour split and an exact card count you spend ages trying to work out the best things to do under the confines of your self imposed restrictions. Certainly having one colour over or under represented changes the draft dynamic but that is absolutely fine if the players are aware of this. It is also very clear that some colours have much more powerful cards and greater depth, by balancing the colours you guarantee some weaker cards will have valuable cube slots over stronger ones. Bigger than 720 cards is unwieldy, a pain to shuffle and more than you could realistically ever need as it supports 16 players at that size. Less than 360 can't support 8 people which is the optimum number for a draft (although 6 is great for team events).
When I come to tweak my cube I simply add and remove cards as I see fit thinking only about their place and role in the cube rather than worry about what to cut etc. The main thing I consider for any card is not the power of the card in isolation but the power of the card in combination with the other cards in the cube. Another way to view this is simply to consider how many different archetypes would want to make use of the card and to a lesser extent the power of that archetype. Many very powerful spells don't have any decks they fit into very well. An example of this off the top of my head is Urabrask the Hidden who is too much mana for aggressive red strategies and too demanding of other support cards to work well in control or ramp based red decks. Urabrask is clearly a lot more powerful than an Ember Hauler but will still see much less play in a cube designed around card synergy.
I keep two piles of cards which I call my B and C cubes ( my main cube being the A cube...) that are simply to aid with tweaking and deck construction. The B cube contains all the cards that have been cut from the A cube, some of which tend to bounce back and forth from A to B as the meta shifts! If when you read my A cube list you find a card missing I can assure you it will reside in my B cube and likely with some reason behind it being there. The C cube contains some really bad cards and is rarely of any use, I just simply stick one of anything that might ever have a use into it which sadly means a lot of really awful tribal cards make up the bulk of it. When playing constructed heads up we have free use on any B and C cube cards to add to our decks should we see fit. This allows the cube to slowly evolve which is nice and also gives the options to make really silly fun theme decks such as a proliferate deck or tribal soldiers or a take on some unusual combo deck that just cropped up such as the new Melira combo.
I have very few gold cards in my cube as they fit into less deck types and so I require a great deal more from my gold cards than a normal card, almost to the point of being an auto include should you be playing a deck of all the appropriate colours. I have an awful lot of land, I think there is more land in my cube than any single colour or artifacts. I have never liked too much of the random element deciding games, the better the mana fixing in your cube the fewer games that will be lost or won by the screw. My cube was powered until about a year ago. The power is very fun but does tend to increase the random factor. I finally cut the power for two reasons, firstly they are all auto includes and thus leave less space in decks for new and interesting fringe cards. By cutting them decks became more varied and games became fresher. Secondly the power, while good in all decks tended to most facilitate the other most powerful cards ever printed, by cutting the power cards like Tinker, Goblin Welder, Yawgmoth'sunpowered cubes.
My cube has a very low average mana cost which furthers its bias as a constructed cube. I also have a habit of throwing lots of weak looking cards from the latest set simply to try them out as every now and again a card really surprises you and becomes a mainstay. Most however get cut directly to the C cube never to return. Periodically one of these new cards on trail never fully asserts itself while also not condemning itself either. A few lingering oddities may be present in the cube lists I offer and this is likely the reason for it. Either that or I was recently doing some constructed style cube and an odd deck needing lots of narrow cards gets made. When I come to discuss each card in detail I will extend this to the B cube as there are many there which need more justification as to their exclusion than many inclusions will need. I shall also provide a B cube list at some point as I find it useful to read others lists for ideas.
Two last points to make on my cube and then we can move onto the cards. Firstly I avoid cards that either hate a colour or an archetype. Games are much more fun when there is no access to pure hate. Secondly, we still play with mana burn because real men play with mana burn.
That concludes a rather piecemeal explanation of the idea behind my cube and should put the present list into an appropriate context which I shall now post.