One technique in meditation that the masters usually tell their students is to look for a gap between two thoughts inside the meditator’s mind. When you meditate, observe your thought at the moment. Look precisely at the point where the thought ends. Then there is a small gap, which might be just an instant, before the new thought begins. My metaphor is usually the stick shift transmission. When you move from, say, gear two to gear three, there is a gap when the transmission is not engaged at all. That’s the gap. It is the period where the mind is “in neutral” so to speak. The mind is not thinking about anything. It is the pure, natural mind.
And this is the goal of shamatha meditation or “calm abiding”. You practice so that the mind become more and more familiar with the state where it is not engaged with anything. Just the mind resting on itself, staying as it naturally is.
So when you found the gap, stay focused on it. Don’t force it; otherwise the gap will fly away and there will be more and more confusing thoughts. Don’t relax it too much either. You could fall asleep.