In India lot of Muslims use to visit graves of Muslim scholars (like Khawaja Moinuddeen Chishti, Nizamuddeen Aulia etc.) I use to oppose my family members asking help from Allah (SubhanauTa'la) through these scholars. I told them you can approach Allah directly without any mediator. But they don't hear. Further some people will quote the Hadith that Hazrat Bilal (Rahmatulla) also asked at Grave of Muhammad Rasulullahi S.A.S. for rain, so why they should be stopped. Please explain this in light of the same Hadith.

Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
Dear brother, asking help, refuge, support etc., from creatures let alone dead persons is not permissible regardless of who they were or what position they held. Allah does not need any mediator between Him and his people and his Prophet did not legislate having intercessors in supplicating or worshipping Allah. Moreover, if this act were good the pious ancestors would have practised it before us. In fact they did not practise it. Allah is All-Hearer and nothing is hidden from Him.
The story of Bilal Bin al-Harith is not correct, so such story can not be used as evidence to prove anything. Even if it were correct we should not follow this pattern since we are obliged to follow what is proved from the Prophet Muhammad (Peace and blessing be upon him) and nothing else.
Allah knows best.