The second question new meditators ask (after what do I do?) is how long
do I do it for? And there is no set answer to that. Five minutes would
be pretty good if you are not currently doing any time at all, but
really, to have an effect it's got to be a reasonable length of time.
Twenty or thirty minutes is a good start: long enough to require some
discipline but not impossibly long. It takes most people a few minutes
to get settled, and to get into the inner routine required. Then you
will need some time to go about your particular discipline, and then to
rejoin the world again. Thomas Keating says, and I think he is right,
that the body seems to have a sort of rhythm that goes in 20 minute
cycles, so blocks of 20 minutes - 20, 40, 60 - works well. It's a good
idea to decide on the length of time you are going to commit before you
sit down. Deciding to finish "when it feels right" is an invitation to
distraction and impatience. Which then raises the question, how will I
know when my time is up?
For those who meditate with their eyes open that's easy. Put a clock of some other timing device (An appropriately sized hourglass, a marked candle, the shadow of the sun on the wall...) where you can see it. For those who meditate with eyes closed, you will need something with an alarm. And that's where your smartphone reveals yet one more function that it's pretty good at. Most phones have a timer function which works just fine, but there are scores of meditation timing apps out there and over the years I've had a look at most of them. Beware of apps which collect information on you, or provide statistics. Meditation isn't a performance for which you or anyone else needs to give you a score. Knowing how many minutes I meditate this week opens me to two traps: that of pride at my success or despondency at my failure. Both of these are potentially fatal to developing a helpful meditation practice.
The app I settled on as the best is Contemplative Outreach's little Centering Prayer app. This gives me a timer with customisable bells; a prayer with which to begin and finish my session; and, for the times when I am not meditating, access to a range of reading materials; and a newsfeed on events being run by Contemplative Outreach.
With a short search of YouTube it is possible to find recordings of people giving instruction in meditation, and I have no wish to judge the usefulness of any of these here - that will depend on the experience and lineage of the instructor, but there is a type of app or YouTube clip which is singularly useless - those which play music or some kind of pre-recorded "guided meditation". While these might be useful as relaxation devices, they are counter productive as aids to real meditation. The aim of meditation is, for a short while anyway, to not be captured and led around by our thoughts. The music or small narratives provided by apps are just that: thoughts, and whatever it is that you are doing when you listen to them, it isn't meditation.