Buddhist philosophy (the Dharma) is very subtle, so there are many ways to understand it and put it into practice. Here, I will argue for what I have found to be a powerful perspective: the Dharma as a guide to lifehacking.
Lifehacking is exactly what it sounds like: finding new, more efficient, and more clever ways to handle day to day life. Just because you do something every day doesn't mean you're good at it, especially if you've never put the time or effort into thinking about what you're doing, how it's done, and how it could be done better. The best thing about lifehacking is that you can begin right now, just by stopping and thinking about the next task you have to perform and whether there is a way to perform it that you haven't thought of before. Remember, the real point of lifehacking is to avoid becoming settling into patterns of activity or problem-solving, so just because you try one new way doesn't mean you stop trying. Keep refining, keep trying new things, just keep thinking and evaluating and you'll be an excellent lifehacker.
Now, the stated purpose of the Dharma is to achieve freedom from suffering. If we want to get technical, we'd want to talk more specifically about what "suffering" means, what conditions would constitute freedom from it, along with a list of technical definitions and demonstrative arguments. Seriously, I could teach a semester-long class on just those formal points and still not cover everything. For our purposes, we can think of the Dharma as having a very simple success-condition: if you are living in a moment without suffering or stress, you have achieved the Dharma in that moment.
That condition may sound too simple. After all, we experience many moments of resting and taking a break where we don't feel any particular suffering but nevertheless feel no particular liberating accomplishment. It's important that we know we've achieved something or else we can't evaluate effectiveness or progress. We need a lifehacker's success condition, so let's try this one:
The Lifehacker Dharma is successful when the hacker experiences the diminishing or elimination of stress or suffering in a situation where stress or suffering is known to manifest.
First Important Buddhist Point: You, the hacker, are the judge of your success. Since you are the one experiencing suffering, you are in the best position to evaluate its presence or absence in yourself. On the one hand, this is the good news because you are not beholden to any authority on how to live your life and whether what you are doing is right or wrong. On the other hand, this is bad news because you are beholden to yourself. Practicing this evaluation requires a discipline to be honest with oneself, brutally so in many cases. The standard is so simple, so foolproof, that the only way to misapply it is to deny it, If you feel suffering but excuse it or rationalize it, you've lied to yourself (well, tried to, anyway). The appropriate response to feeling stress or suffering is to look at its causes or triggers, bringing us to a the Second Important Buddhist Point...
Second Important Buddhist Point: Everything that happens has a cause. There is no true spontaneity. Randomness is conditioned, "free will" is conditioned, events occur because other events have already occurred, etc. Likewise, thoughts, feelings, emotions, and attitudes are conditioned; they can be triggered by external events or internal events, and they can be diminished or eliminated in the same way. There is no downside here because anything that manifests in dependence on some cause will cease when its depending condition ceases. Stress is a feeling, so it occurs when triggered. When another feeling is triggered, it can overwhelm the feeling of stress, depending on the relative strength of particular instances of feeling (which depends on the strength of the triggers, which depends on...well you get the idea). So, to confront feelings of stress, you begin by looking around for causes and triggers and figuring out what do about them. Here, we have to add one more important point.
Third Important Buddhist Point: There is nothing spooky about causation. We may not be able to observe every cause or condition directly, we may not have specific knowledge about the fine details of every situation, but relations between events are nevertheless knowable. We can look at an immediate feeling, find its proximate trigger or depending condition, and address that trigger or condition. Doing this well takes practice and discipline. We have to be willing to look, habituated to paying attention, and honest about our observations. When we have a clear idea of what feeling is in focus and how it came to be in focus, we know more about our emotional lives. Knowing more about relevant causes and conditions (including which are relevant) gives us more power to influence our lives and feelings.
For the rest of Buddhist lifehacking, just put these points into practice. Practice self-reflection and evaluation, being honest with yourself. Reflect on your perceptions and observations, noticing the triggers and changing conditions that yield pleasant and unpleasant results. Finally, remember that the conditions most important to notice are the ones that are present and available to immediate perception, not the unseen or mysterious. It's a process of continual reevaluation, assessment, and reflection. If you're not happy, start looking at how you are feeling, and what triggers those feelings. Look for triggers that turn your emotions around, and do what you need to do. Don't accept unhappiness. It's a problem in need of a solution, not a necessary state of being.