There's an overabundance of folks here who can, and will, give lots of technical expertise.
That's not me.
I'm going to suggest that your preparations also include a spiritual aspect/grounding. I personally am not a fan of the recreational view: of taking any given substance and hoping for the best.
It's my experience that the mental, and spiritual state of a person is perhaps more important than the technique of how it gets ingested.
Given enough time, and trials, your technique will be honed. You will find the elevation you're looking for. Yet finding proper rituals in preparation of your voyage should be simultaneously honed as well.
In the sense that driving a car is more than simply putting it into gear and then blindly driving, ingesting an entheogen is something that should be taken seriously...
or as seriously as one would be behind the wheel of a large automobile.
So, being prepared is extremely important.
I personally view a voyage while on psychedelics and entheogens as a path to knowledge. Preparing for a voyage on an entheogen is preparation for taking a trip to knowledge.
There's plenty of things in this life which are legitimately fun. If one is simply looking for a fun time, perhaps boating, or cycling would fit the bill. Ingesting an entheogen for "fun" is likely to have undesirable consequences.
Ok, so what kinds of spiritual preparations should one make?
These are all suggestions:
Invocation.
To invoke the help and aid of whatever benevolent entities are there to help in the human's growth. Assuming you know the time and place you'll do this, then make a reservation with your Higher Self, with whatever benevolent entities are there to help you in your search for knowledge; a reservation with them to attend you and watch over you.
Fasting.
While nutritional fasting is recommended, it is optional. Mental and spiritual fasting are extremely important to me. This would be a personal ban on watching, or listening to things not intended to encourage your spiritual growth. Such things to avoid are those showing, glorifying the excesses of society, things extolling greed as a virtue, for example. One can not "unsee" anything, so s/he should be careful on the mental and spiritual intake prior to a voyage.
Personal inventory.
Again optional, but highly recommended. The idea is to uncover and to deal with those elements of one's personality which the one has tried to keep hidden. DMT, in all it's various forms in my experience, are like truth serum. No thing lay hidden while inside the field of the vegetal, or the DMT flash. The DMT will allow one to resolve the issue, yet issues can't get swept under the rug, with desirable consequences.
Setting.
Sure, we talk a lot about setting of the place to do the blast-off. All of which applies here. What I am going to say about the setting is that prior to blast-off, it is strongly suggest, and highly recommended to establish a safe perimeter within which is the field of your experience. On a real, physical level, it is important to establish the "safe perimeter", and to declare with clear intention, where the boundries, physically, of your experience will be. If this voyage is to take place out in the woods (truly ballsy!!), then in the course of establishing your perimeter, it is wise and advised to use the trees as your sentinels, the guards who physically watch over you as you blast-off. Giving the trees names, and describing what of them you what them to do, to me have been important in keeping me safe during these times.
Positive mindset.
It's not the physical presence of the trees themselves which keeps you safe and secure. Yet it is the establishing of this perimeter, with the force of consciousness applied to the situation, which keeps one safe. Consciousness runs the day, when in the Astral realm. Spoken forth on Earth, causes to to be so in "the heavens." The equation is: as above, so below. Speaking forth the perimeter, also comes with the necessity to envision, picture-forth what you want to see happen.
Using benevolent forces.
A positive mindset applies during the voyage as well. If one has made solid preparations in this respect, then calling-forth the benevolent entities DURING a voyage becomes no problem, as they will already be there, and ready to usher you into a sacred space of growth: of love, light and wisdom.
Set your grounding cable.
When, or IF, things get rough, then it is important to picture a grounding cable attaching you to the middle of the Earth. If you can, picture a cord of pure white light, infinitely strong, which is attached on one end to your solar plexus, or your heart center, which then travels through the planet, extending all the way to the core, which is then affixed to a large precious gem: a diamond perhaps, or huge ruby, or sapphire which is perhaps the size of a basketball anchored into the center of the Earth. Before blast-off, it is highly suggested to picture this grounding cord, at work; feel its effect. If/when things get rough, picture this cord at work, grounding you to Earth, to the love of our Mother.
An analogy may be helpful.
I am told that entheogenic substances, whether it be LSD, DMT, hoasca or other, are portals. These are inter/hyper-dimensional portals where one travels to anytime, anyplace.
Often this is what happens. Someone taking a recreational voyage winds-up "anyplace"; which is to say: in the wrong place for that person. Taking a voyage through this portal allows one to share the consciousness and experiences of all those who have ever taken the substance--to good, or bad effect.
Because of the non-locality nature of these substances, one can share in another's trip--for good or bad. The unpredictable nature of recreation is this way, that there's not a guarantee you'll be happy where you land. Without any spiritual or mental preparations, the "vehicle of departure" is quite likely to take you to a strong experience had by another person/being. This is akin to getting on the wrong train and it taking you to...where ever.
I personally am not a fan of the "wind-up wherever" approach to ingesting an entheogen.