1.) Make salaam

2.) Recite these du’as:

أَسْتَوْدِعُ اللَّهَ دِينَكَ وَأَمَانَتَكَ وَخَوَاتِيمَ عَمَلِكَ

I give in Allaah’s trust your religion, your belongings and the result of your deeds.  

(Abu Dawud, Tirmidhi)

Salim ibn ‘Abdillah ibn ‘Umar [Rahimahullaah] narrates that when a person intended going on a journey, ‘Abdullaah ibn ‘Umar [RadhiAllaahu Anhu] would say to him, “Come near me so that I may bid farewell to you just as Rasulullaah [SalAllaahu Alayhi Wasallam] used to bid farewell to us.
He would then make the above supplication. (Tirmidhi no. 3443)

زَوَّدَكَ اللَّهُ التَّقْوَى، وَوَجَّهَكَ فِي الْخَيْرِ، وَكَفَاكَ الْهَم

May Allah make taqwa your provision, may He turn you towards goodness, and may He suffice for your worries.

 ‘Abdullaah ibn ‘Umar [RadhiAllaahu Anhu] narrated that a young person went to Rasulullaah [SalAllaahu Alayhi Wasallam] and said, “I intend to perform Hajj this year.
Rasulullaah [SalAllaahu Alayhi Wasallam] then made the above du’aa.”
(Amalul-Yaum Wal-Lailah of Ibn Sunni no. 506, Al-Mu’jamul-Awsat no. 4548)

3.) Ask those going to the blessed lands to supplicate on your behalf.
‘Umar ibn al-Khattab [RadhiAllaahu Anhu] narrates, “I sought permission from Rasulullaah [SalAllaahu Alayhi Wasallam] to perform ‘umrah. He granted me permission and said, ‘O my brother! Do not forget us in your supplications.’
This statement of his was such that I would not like the entire world in exchange for it.”
Another narration states that he said: “O my brother! Include us in your supplications.”
(Abu Dawood no. 1498, Tirmidhi no. 3562)

4.) Give him some advice and when he leaves, then supplicate for him

اللَّهُمَّ اطْوِ لَهُ الأَرْضَ، وَهَوِّنْ عَلَيْهِ السَّفَرَ

O Allaah! Shorten the distance for him and make the journey easy for him.

Abu Hurayrah [RadhiAllaahu Anhu] narrates that a man said, “O Rasulullaah! I intend embarking on a journey, so please advise me.”

He said, “Hold on firmly to the fear of Allaah, and say the takbeer (Allaahu akbar) at every elevated place.”

 When the man turned and departed, Rasulullaah SalAllaahu Alayhi Wasallam supplicated, “O Allaah! Shorten the distance for him and make the journey easy for him.” 
(Tirmidhi no. 3445)

5.) Have the desire in your heart to be with the hajees and join them, even if you are unable to do so.

Anas ibn Malik [RadhiAllaahu Anhu] narrates: We returned from the battle of Tabook with Rasulullaah SalAllaahu Alayhi Wasallam when he said, “There are some people behind us in Madinah. We did not traverse any pass nor valley without their being with us [i.e. they shared the reward with you]. Some valid excuse kept them behind.”
(Bukhari no. 2839)

6.) Make du’aa in general for all the hajees.

اللهُمَّ اغْفِرْ لِلْحَاجِّ , وَلِمَنِ اسْتَغْفَرَ لَهُ الْحَاجُّ

O Allâh, forgive the hajees and those for whom the hajee has sought  forgiveness 
(Musannaf ibn Abi Shaibah, Sunan Kubra of Baihaqi, Hakim)

Umar [RadhiAllaahu Anhu] said that those who go for Hajj as well as those who seek forgiveness for them are forgiven for the remainder of Dhul-Hijjah, Muharram,Safar and ten days of Rabiul Awwal.
(Musannaf ibn Abi Shaibah no. 12657