Do not slouch. When you are meditating, it is essential you maintain proper posture. This means that your back is well aligned. There are two reasons for this. First it allows you to breathe in and out properly. Breathing is an important aspect in meditation since it brings you to the present moment and it allows proper circulation of the blood, which, in turn, relaxes you. Second, correct posture permits you to last as long as you can during meditation.