Zikr after salah

Whoever glorifies Allah (says Subhaan Allah) thirty-three times immediately after each prayer, and praises Allah (says Al-hamdu Lillaah) thirty-three times, and magnifies Allah (says Allahu akbar) thirty-three times, this makes ninety-nine, then to complete one hundred says Laa ilaaha ill-Allaah wahdahu laa shareeka lahu, lahu’l-mulk wa lahu’l-hamd wa huwa ‘ala kulli shay’in qadeer (There is no god except Allah Alone, with no partner, His is the power and His is the praise, and He is Able to do all things) – his sins will be forgiven even if they are like the foam of the sea.
Sahih Muslim, Book 4, Number 1243

As regards counting tasbeeh, the Sunnah is to use the fingers of the right hand, although it is permitted to use the left hand. The evidence that the right hand is preferable was reported by Abu Dawood (may Allaah have mercy on him), who said: “ ‘Ubayd-Allaah ibn ‘Umar ibn Maysarah and Muhammad ibn Qudaamah, among others, told us: ‘Aththaam told us from al-A’mash from ‘Ataa’ ibn al-Saa’ib from his father from ‘Abd-Allaah ibn ‘Amr who said: ‘I saw the Messenger of Allaah (peace and blessings of Allaah be upon him) counting the tasbeeh.’ Ibn Qudaamah said: ‘With his right hand.’” (Sunan Abi Dawood, Kitaab al-Salaat, Baab al-Tasbeeh bi’l-hasaa).

It was said in Haashiyat al-Tahtaawi: “It is correct that he (peace and blessings of Allaah be upon him) used to count the tasbeeh on his right hand. It was reported that he said: ‘Count with your finger tips, for they will be asked and they will be made to speak.’ Ibn Hijr said: Counting the tasbeeh with the fingertips is better than using the subhah (prayer-beads or “rosary”).

The sunnah is to count with the fingertips by putting them on the palm of the hand.