TM, transcendental meditation involves being given a specific mantra by a TM master. This is usually a word that you focus on during the meditation for 20mins twice a day. It works if you work it as with most things. You can choose a word, like 'focus' or 'love' to meditate on even if you haven't been given an official mantra. Or you can simply visualise the flicker of a candle flame in your minds eye.
Mindfulness is the most useful meditation form I've found to help me. It is not a dedicated time that you 'do' meditation, but a greater awareness of yourself and all around you as you go through life. It is becoming the observer. Simply by noticing your thoughts and noticing yourself noticing your thoughts it can bring about a much higher level of clarity.
The great thing with this is you can set up certain triggers to remind you to do it. There are several apps that can ding at a random interval and remind you to become aware. Or you can use walking through a doorway as your trigger.
For me personally, I want to improve my levels of patience. So now any time I feel impatient, I use that as my trigger to become present to where I am, what I'm feeling and how I'm being.
Being impatient is essentially rejecting the reality of 'now' for some preferred future. So by coming back to experiencing the present moment as if I had chosen it myself, it's quite a powerful way to then move forward.
Best book I've read that can help with this is Power of Now by Eckhart Tolle.
There are many kinds of visualisations, breathing techniques, silence and stillness exercises, but the most useful to actually making a difference in life is mindfulness from my experience. And the great thing is it doesn't take any extra time out of your day!
I prefer algebraic meditation, so I meditate on √2 instead.
EDIT: This was downvoted within two minutes. Get a sense of humor, HN.