It seems that 99% of the discussions and instructions on "how to rogue" are focused on 2 things: gear and spec. The implication is that if you stack enough +hit, choose the right talents, and memorize your cycle (3s,5r or whatever) you're done. I may eventually talk about talents and gear, but initially my objective is to talk about what you can do to maximize dps once you've got the right talents and gear.

Energy Optimization

The problem with relying on a "cycle" is that energy generation is never consistent. Some factors that can affect energy generation and thus your cycle:

1. Relentless Strikes always gives you 25 energy on a 5 point rupture, but if you use (for instance) 3 points on Slice & Dice, you only have a 60% chance of getting energy.
2. Likewise Ruthlessness always has a 60% chance of giving you a point, and you may have 4/5 T4 for a 15% chance of another.
3. Blade Flurry uses up 25 energy every 2 minutes.
4. If you have Riposte and for some reason in procs (i.e. you catch a cleave) that's 10 energy well spent but 10 energy nonetheless.
5. Of course Combat Potency is utterly unpredictable, further complicated by the fact that haste bonuses (DST, Bloodlust, Haste pots, Mongoose procs, Blade Flurry) increase its proc rate.
6. You may have something like Rod of the Sun King that occasionaly gives you energy

All of those factors (except riposte) can be modeled to determine your average energy gain per second in a sustained fight, but on a moment by moment basis "average" isn't very helpful. So in reality the process of optimizing energy usage is never as simple as "3s/5r". Instead you have to be able to think ahead a few seconds and plan out how long is left on slice & dice, how many combo points you have, how much energy you currently have, etc.

Here are some guidelines to try to follow:

1. You never want Slice and Dice to run out, but you also want to avoid overlapping it. Ideally you want to refresh Slice & Dice exactly as the last one expires. If you overlap by, say, 3 seconds you've wasted a portion of both the combo points and the energy you used.
2. Likewise neither do you want to overlap your Ruptures. Wait till one ends before starting the next one. (If you try to overlap and the previous one was applied while you had a temporary AP boost, say from a trinket or something, you will get the "A more powerful effect..." error message.)
3. Avoid spending 5 points on Slice & Dice. Because you get 9 seconds for 1 point and 3 additional seconds for each additional point, your "seconds per point" decreases with additional points. However, there is also an energy cost to Slice & Dice (25) so while a one point S&D may be very efficient from a point perspective, it is inefficient from an energy perspective. Rule of thumb is that 3 is optimal and that 2 or 4 are ok. The one exception is on your opener: get S&D going right away instead of being tempted to burn all your initial energy on big hits.
4. Never, ever, ever let your energy bar reach 100 for more than a nanosecond. If it's sitting at 100 you are wasting energy.
5. Conversely, try to avoid draining your energy bar to zero by spamming attacks unless you are doing so with an intentional plan to optimize energy. Example: 2 seconds left on S&D, 2 combo points up, 45 energy: you sinister strike (5 energy), wait for tick and for S&D to run out at the same time (25 energy), Slice & Dice. Another example is that you know you're about to go out of combat range (Illidan parasites, Archimonde's Air Burst or fear, etc.) so try to get your energy down to zero so as to waste as little as possible.

Again, the key is to look ahead and think about how much time is left on Rupture and S&D and how much energy you have and simply plan ahead a little bit. Don't adhere to strict cycles and focus instead on using energy efficiently

Coming up next: Positioning