When starting meditation there are a few things that will help you to concentrate.
Create a quiet environment around you. Take care that you won't be disturbed for the duration of your meditation. Have your Silatha Dorje close to you, as you will use it during the meditation session.
Take an active and comfortable position.
When you sit cross-legged, to be comfortable, your knees need to be levelled to your pelvic floor or lower. Sitting on a pillow helps your back to be straight and allows the spine to be free.
A straight spine is key; if you are wobbly your mind might drift off. Mind and body are intertwined. It is easier for your mind to be in balance if your body is balanced well. To straighten up, adjust your upwards position, gently tilting your chin inwards to feel the stretch behind your neck and elongating your spine as if an invisible cord was pulling your spine up from the top and down from the bottom, making space between each vertebra.
Another comfortable position is to sit on your knees, bending your legs on each side of the pillow.
If this is still strenuous, then sit on a chair so that the posture isn’t a distraction for you. Make sure your feet are touching the ground and your spine is straight.
Let the muscles in your shoulder and back relax. Your shoulders can be pushed slightly back. Slightly tuck in your chin. Bring a sense of relaxation to the muscles in your face so that your jaw hangs open. Place the tongue up against the roof of your mouth to allow for clear breathing and slow down the swallowing process, which can at times be distracting.
Relax your gaze in an unfocused manner. Ideally pick a point on the floor about two meters in front of you. Do not pick out patterns or define shapes, just maintain a small opening, to let some light come in. This way, chances of falling asleep are slimmer. When you leave a small opening, for the first time it's likely that your eyelids will vibrate very quickly. This will stop after a while. If this distracts you, keep your eyes closed. It’s good to experiment and see what feels best for you.
Enjoy your Silatha Journey!