I’ve come to the realization that in most of the armies I design (with 6^th edition and the current meta in mind), I try to create many different deployment options. This allows me to always react to my opponent, which in turn allows me to always have positional advantage. Andrew Gonyo demonstrated the importance of going second in this article, which does a great job of highlighting all the main reasons to go second if given the option.
However, 40k is a dice game, and roughly 50% of the time you do not get the choice. Part of the challenge of 40k is implementing tactics and building lists to mitigate the opportunities for dice to screw you―this especially includes the roll for turn order. By creating a list that emphasizes multiple deployment options, you can certainly ease the pain of going first.

Reserves
Reserves force your opponent to play differently; without knowledge of where your army is, your opponent will have to be cautious and keep up a strong defense on all sides in order to not get blindsided. This will severely limit his offensive capabilities as well as his ability to spread out for board control. Also, when you go first with a reserve-based army, your opponent will lose half the advantage of going second, which is the ability react to the enemy’s deployment. If most of your army resides in reserve, you can play cautiously and limit the amount of firepower you take, then come out of nowhere and decimate the enemy by coming in at his weakest point, or surrounding him and giving him no place to retreat.




Alpha Strike
Having the capability to Alpha Strike the enemy is also a wonderful tool for a 40k player. The term Alpha Strike means to deal a massive, crippling blow to the enemy on turn one (sometimes turn two), then pressing the advantage gained early on to carry out the win. Armies with large scouting opportunities or incredible firepower (White Scars, Ravenwing, Tau, and Dark Eldar) are the primary armies for Alpha Striking, although almost all armies can Alpha Strike to a lesser degree.
Often times however, it is not the Alpha Strike that will win you the game; it is merely the threat of being capable of launching one. If your opponent is aware of what your turn one damage output can be, he will deploy incredibly cautiously (even if going first, in case of seizing), which will immediately give you board control and allow you to outmaneuver the enemy army.

Rapid Redeployment
Rapid redeployment is the last step of having multiple deployment options. The idea here is basically to trick your opponent. Your army is designed to be so incredibly mobile that you can fake your opponent out by deploying in one section of the board and moving (and often turbo-boosting or moving flat-out) to the opposite side. After you have completely outmaneuvered the enemy, you can start taking his army apart piecemeal with the longer-ranged elements of your own.
One of the reasons Eldar are currently dominating the tournament scene is that they have the ability to play in all three deployment options. Eldar armies often reserve loads of Jetbikes, Spiders, and Swooping Hawks to come in and harass unprotected scoring units. Eldar are also very capable of conducting Alpha Strikes with multiple Wave Serpents, Wraithknights and the ever popular Tau allies. And lastly, they are easily the fastest army in the game with the ability to move their Jetbikes and Seer Council 48”, Wave Serpents 36”, and even put their Swooping Hawks back into reserve to re-enter them using Deep Strike on later turns.
It is clear that 40k is, to at least some degree, won and lost in deployment. Based on results found in Torrent of Fire’s Ultimate Weapon, Eldar seems to be one of the armies dominating in the deployment phase; however; other armies are capable of competing with them. I think the new and underused Space Marine codex is the army to do it