This is an attempt to give some advice for those that either don't have a teacher, don't want a teacher, or those who will maybe look for a teacher in the future but don't want one at the moment.
For this to work several things are needed. Patience and discipline are two of the most important. With meditation that doesn't have a teacher, extra emphasis needs to be placed on this. If you don't have patience, you won't carry on until you see the benefits. If you're not disciplined, you'll not meditate consistently enough.
Another important part, especially seeing as there's no teacher, is that the meditator has confidence in his/her ability to gain insight into the nature of the mind, and the nature of what we think of as reality. Without confidence, all of the positive aspects that are hoped to be gained will be tainted with doubt. Doubt is a hindrance, and there should be an awareness of this.
The meditator also needs the awareness to know whether or not s/he is progressing. This isn't easy and delusion can and probably will be an obstacle at several stages. Without the awareness to see this, which should be developed as meditation is done over time, the meditator will be lost. A teacher usually acts as the awareness of how the student is progressing or not, then directs the student towards understanding that so that s/he can continue progressing, or correct the errors that are stalling the progression. So without a teacher awareness is one of the keys. If the meditator can't develop enough awareness then maybe it's best to seek a teacher for guidance instead.
Skill is also needed. Skill here meaning the act of refining the ability to do the types of meditations that are chosen, and also finding the right types of meditation that are best. Also gaining the right insights from the meditations.
A set of qualities should be emerging as the meditator progresses. Some of these qualities are an increase in = awareness, concentration, unattachment, equanimity, egolessness, serenity, and metta (kindness). Others are what was mentioned above, like skill, patience, and discipline.
The root of the problem being aimed at, or the understanding of why the meditator has the goal of awakening is that most of us are in a way, asleep. We don't properly understand how what we think of as "reality" works, and how to live in it properly without being free from things like stress, delusion, anger and greed. We don't understand balance in the way we should, or what the Buddha would call "The Middle Way." The aim is to try and wake up and understand what these things mean, and in a sense, be those things. The balance, the middle way, the understanding, the realisation, and so on, as we live our lives. Free from delusion, anger, greed, stress, and all the variations of those negative aspects.
For those familiar with the concept of karma : maybe experiment with reducing karma from time to time, by not creating events or adding to certain events. Clearly if someone needs help with something that isn't causing others any problems, then try to help, but experiment with other situations. Karma is action, and the more actions we take part in the more we become attached to the world. To learn meditation properly it's often said that there has to be some type of withdrawal from the world, even if temporarily. So experiment with it in the right situations. Say for example you're going to do something because you're bored : try not doing it and see what happens. See how it makes you feel, think, perceive, and so on.
Remember that even reacting to something as small as a thought, feeling, or perception can be classed as an event. To react is to add to an event, to take an action, which is karma. The reaction could also be seen as creating a new event in response. It can be hard to describe, but so many things are linked together. Try just noticing what's happening instead. You could even say noticing is an event, but to think like this could go on infinitely! Remember that you're just trying to reduce karma, reduce action, by not creating or adding to some events, and then noticing the way you are as a result of that over time.
By doing this properly you could increase the chances of being unattached to your surroundings, habits, thoughts, feelings, perceptions, and other things, and become better at meditating. Equanimity helps with this. If you're not sure what that is, maybe try researching into it.
This whole process isn't supposed to be easy, especially not without a teacher. If it can be done though, or even if a meditator can progress and learn before eventually finding a teacher or the right school, it's worth trying.
Another thing is research. Research the types of meditation that are chosen. Research how they're done via several different sources, their history, and also the school or tradition they come from if possible, to get a better understanding of the meditations and their origins.
This obviously isn't a perfect description of how to meditate, but hopefully it can be of help to those without a teacher in some ways.