All praise is due to Allah, prayers and peace be upon His Messenger.
Aisha (may Allah be pleased with her) reported: “Whenever Allah's Apostle took the bath of Janaba, he cleaned his hands and performed ablution like that for prayer and then took a bath and rubbed his hair, till he felt that the whole skin of the head had become wet, then he would pour water thrice and wash the rest of the body." {Al-Bukhari (284) & Muslim (316)}.
Aisha also said: “Whenever the Prophet took the bath of Janaba (sexual relation or wet dream) he asked for the Hilab or some other scent. He used to take it in his hand, rub it first over the right side of his head and then over the left and then rub the middle of his head with both hands.” {Al-Bukhari (258) & Muslim(318)}.
A complete valid Ghusl includes the following :
1- Intention
2- Mentioning Bismillah ,washing the hands thrice and washing the private parts.
3- Making ablution (like that for prayer).
4- Pouring water on the head thrice till the whole skin of the head becomes wet.
5- Washing the right side of the body ,then the left side and rubbing water with hands over the whole body.
6- It is desirable to use soap or the like while bathing in order to achieve cleanliness.
However ,Ghusl is valid and major impurity is removed if one desires not to perform complete Ghusl provided that he/she abides by what follows :
1- Intention to cleanup impurities : janaba ,menstruation ,and nifas (puerperium).
2- Washing the whole body so that water reaches every spot, and the hair is rubbed until the whole skin of the head becomes wet .And Allah Knows Best.