All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
Visiting graves is Islamicaly recommended; this is based on the Hadeeth where the Prophet, sallallaahu ‘alayhi wa sallam, ordered us to visit graves and said that they remind their visitors of the Hereafter. [Muslim]
However, the visitor must avoid impermissible acts of Shirk, Bid‘ahs (religious innovations) and prohibited speech.
With regards to sprinkling water and putting grains on graves, such acts have no basis in Sharee‘ah. Rather, they are Bid‘ahs and are of no benefit to the dead, who only benefit from supplications to Allaah to forgive them.