Well....nice tips...just one addition....well...it's my point of view anyway:
It is a medical fact that the human brain can only continuously work/memorize/learn for 90 minutes; after which the brain becomes unweary and can not gain and whatever is learnt or read is not that easily comprehended or stored. Therefore a break after 90 minutes of continuous study is absolutely essential. This break can be of 15 minutes or so; so as to recharge the batteries. A break of a minute or so after every 20 minutes isn't a problem...taking a break of 20 min after every 20 min is a problem....if u know what i mean...