Start very small, only 5 minutes. Good timeslots are: first thing in the morning, after lunch, before bed.
When getting started I believe the simplest way is to focus on the breath. Putting aside the fact that this can become a hinderance at more advanced levels, it is by far the most beneficial, tangible and reliable method I've seen.
I would recommend a few breath paradigms, all of which require diaphragm breathing:
Take slow, controlled breaths, counting up to 10
Keep both the inhale and exhale smooth
Breath in for a count of 4, hold for a count of 7, breath out for a count of 8
Breathe in for a count of 10, breath out for a count of 10
The Wim Hof method
I'm just barely playing with this
Big tip: practice breathing through your nose as often as possible / practical.
Beyond the basic relaxation and/or health effects of deep breathing, we're aiming to sharpen the mind's ability to focus. When we lose focus on the breath and find ourselves lost in thought, we repeatedly come back to the breath. Here are some aspects of breathing to help focus on:
The rising and falling of your chest
The movement of your abdominals / stomach
The movement of your shoulders
The feeling of air in your nostrils and sinuses
The feeling of air in your throat
The precise sensation of air moving past the opening of your nostrils
This should be more than enough to occupy you for 1-3 months of practice, increasing session length up to maybe 10 minutes.
Use reminders throughout your day to take a few deep breaths
Making a cup of tea
Standing up from your desk
Getting out of the car
Sitting down on the couch
Getting in the elevator
Try appreciate how relaxed you feel after a session
Then, try to notice when you become flustered, anxious or irritated and contrast the experience
How does the body feel?
Now we've established the basic ability to focus on a "Meditation Object" (a.k.a the breath). Our next goal is to take this ability to focus and point it at any sensory experience. Broadly speaking there are six categories of sensory experience we can focus on (this is lifted from the work of Shinzen Young):
Sidenote, you may expect we would call the breath the subject of meditation rather than the object. The reason for this distinction is that you are the observer of this object, making you the subject of conscious experience. This may help you understand strange terms like the subject-object gap and non-dual awareness when you come across them.
What you hear
What you see in front of you
Back of your eyelids
The spectrum of colour and light
This one is tricky
Talking to yourself in your head
Visualisation ("The Mind's Eye")
My routine for this phase involves picking one of these as the main focus of each session. I find that they increase in difficulty as follows:
The practice remains the same regardless of the object. We notice the finest detail we can about the sensory input without letting our attention collapse into the object. This is a strange and difficult distinction to make for many, don't worry if it's tricky. There are techniques for getting the hang of it.
If you've started to get comfortable with a few of these, try combining them. Some simple combinations are:
following the breath + paying attention to sounds
feeling the body as a cloud of sensation + seeing the back of your eyelids
When it comes specifically to emotional state, I would advise practicing Metta meditation. I see nothing wrong (and a lot right) with practicing being a nicer, more compassionate person, and this shit works. A useful tip for Metta is to focus not only on the mental state but the physical sensations accompanying love and care. Feeling these in the body is a reliable way to bring them to the front-of-mind during your daily life.
Altered states of consciousness
"Glimpse" practices (DuckDuckGo it)
It can be hard to explain this stage without defining our terms:
Attention or Focus is the ability to keep concentrating on a Meditation Object without becoming distracted and identified with thought
Awareness is the full spectrum of all input available to you at any given time
To use a more concrete metaphor: attention is like the spotlight on a stage, narrow but bright. Awareness is the lighting in the room itself. We aim to move our efforts from cultivating attention to awareness in this phase. That is to say, brightening the lights in the room until we can see it all at once.
I found this stage incredibly difficult. It took a huge amount of reading and learning before I made any progress. I cannot give you a guaranteed method to make this click for you, it might even be very easy for you!
I once again found Shinzen Young invaluable during this phase. He helped me view consciousness itself as a container or "bubble" containing the entirety of my experience. Sam Harris also pushes these same buttons in his Waking Up app. I sometimes think of myself as being suspended within this bubble, and meditation is trying to push my awareness out to the boundaries. This is often accompanied by a sensation of "standing behind myself". Effectively, consciousness and its contents shift to become one all-encompassing meditation object.
One of the major turning points for me was understanding that rigid focus and determination are actually impediments to putting all the pieces together. Accordingly, letting go is the theme of this phase. Dropping your brow-furrowing focus and trying to find the underlying background awareness is key.
I accomplished this by bringing together all 6 of the input streams mentioned in Phase 2. I would rigidly concentrate on each, adding them one at a time, and then suddenly drop my effort and look for the commonality between them. I repeated this over and over until I started to "drop in" to that underlying layer. This was accompanied by new experience, such as remaining aware of sounds, sights and breathing while having full-on conversations with myself (internally, of course).
Sidenote: this is where self-dissolution and non-dual awareness come into the picture. When you glimpse being aware of the entirety of conscious experience... There's no room left for "the ego" in that moment.
In my opinion, this is where things really changed. I found it much easier to carry this sensation into everyday life and it has been a massive aid for my self-care, professional life, relationships and general happiness in life.
This is where I am today. I have not mastered the preceding phases, but this is my frontier of learning.
We've started to poke at the shape of consciousness itself. The container of all experience. Our pursuit is now as much intellectual and philosophical as it is experiential.
Until this point I found concepts such as Zen Buddhist Koans absolutely nonsensical. Eventually, via Terrance McKenna, I heard of "the fallacy of misplaced concreteness" (Alfred North Whitehead) and things started to click. Our model of the world and our perceptions of reality are only the vaguest approximations of truth. The rigid structure we attempt to place upon reality is not reality itself, merely one representation of it.
Question every hard rule about how to live and perceive the world. Do not confuse this with science denial, this is the perspective I would hope to see from our leading scientists. Never assume we fully understand, we can merely observe and attempt to predict. Be highly skeptical of anyone pushing certainty upon you, including me.