Salaah is the greatest of the practical pillars of Islam.It is the act that separates between one and shirk (The Prophet(PBUH) said:'Between a man and shirk i.e what protects him from shirk,is the abandonment of salaah[Muslim]).Allah(S.W.T) said in the glorious Qur'an :'..,and stand before Allah with obedience'[Q2:238]
As for khushoo'(humility) in prayer,it is a part of salaah that most of us have neglected in our obligatory and supererogatory prayers.Some of us just imitate the imam physically by following only his gestures.If you may ask somebody the surah that was recited in a particular salaah(eg maghrib) ,he may not be able to reply correctly.This as a result of negligence of khushoo'.
Some of the ways one can develop khushoo' in his heart during salaah are as follows:
1.Preparing oneself for prayer properly(performing ablution properly,repeating the words of adhaan after the muazzin,siwaak etc)
2. Moving at a measured pace during prayer i.e no hastening
3. Remembering death whilst praying
4.Pondering over the verses and invocations being recited.(Here,the knowing the translation of the verses and also Qur'anic exegesis is advantageous).
5.Reciting in a slow,beautiful and rhythmic tone
6.Praying with a barrier in front of one
7.Placing the right hand on the left hand on the chest
8. Looking at the place of prostration
9. Moving the index finger during tashahhud
10.Seeking refuge with Allah from the Shaytaan
The above are just some of the means for developing khushoo.For further reading,you can consult
1. 33 ways of developing khushoo by Shaykh Muhammad Salih al-Munajjid(downloadable in pdf form from kalamullah.com)
Any useful contribution is welcome