This is the traditional meditation posture. Both feet rests on the thighs. This requires considerable flexibility of the legs and may be difficult for most people without proper training.

This posture is easier than the full lotus.The right foot rests on the left thigh. The hands rest on the lap with palms turned upwards. The eyes are kept lightly closed.
This is a fairly easy posture. The legs are folded and both feet rest on the floor. Sitting on a carpet or a folded blanket will ease the pressure on the legs.

Using a cushion
A cushion about 4-6 inches high will be helpful to maintain above postures.
It is important not to lean against the wall and to keep the spine straight, which helps concentration.

Using a stool
Those who find it difficult to sit cross legged can use a stool or a straight back chair