There are thousands of meditation methods and a beginner like you will naturally get confused which to choose for the best results.
Let me suggest a very simple guideline to adopt for a holistic well-being:
Level 1: For physical well-being
Meditate on your breath or the bodily sensations.
Contemplate on physical problems.
Level 2: For mental/moral well-being
Meditate on thoughts and emotions.
Contemplate on moral issues.
Level 3: For spiritual well-being
Meditate on the image of a guru or god, or on the supreme God.
Inquire: Who am I? Where is God?
Frequency: Make a routine, but stick to it.
In the beginning you can spend less than 15 minutes per day, but you have to follow it. Gradually increase this time and move from Level 1 to Level 3.