Solah Tasbeeh is done with 4 rak'at of sunnah prayer. For the Sunni with Syafie Mazhab, we use to do it with 2 Salam, that is 2 rak'at prayer then salam, then 2 more rak'at prayer then salam.
The other important thing in this Solah is, the saying of Tasbih (Subhanallahi Walhamdulillahi wa La ilaha illallahu Wallahuakhbar) 300 times. 75 Tasbih in each Rakaat.
Ibnu Abbas RA narrates that Rasulullah SAW said to Abbas:
O 'Abbas! O my uncle! Shall I not give to you? Shall I not present you? Shall I not give to you? Shall I not tell you an action if performed, you would get ten benefits; Allah will forgive your sins, the past and the future, the old and new, (committed) unknowingly and knowingly, minor and major, secret and open? You should offer four Rak'at reciting in each one Surah Fatiha and a Surah, and when you finish the recitation in the first Rak'at, you should say fifteen times while standing (Qiam): Subhanallahi Walhamdulillahi wa La ilaha illallahu Wallahuakhbar. Then you should perform Ruku', and say it ten times while you are in Ruku'. Then you should raise your head after Ruku' and say it ten times while standing (Iktidal). Then you should go down in Sajdah (Sujud) and say it ten times. Then you raise your head from Sajdah and say it ten times while sitting (sit between two sajdah). Then you should perform the second Sajdah and say it ten times. Then you should raise your head and say it ten times while sitting. That is seventy five times in every Rak'at. You should do that in all the four Rak'at. If you can offer this (Solah Tasbih) once daily, do so; if not, then once every Friday; if not, then once a month; if not, then once a year; if not, then once in your lifetime. (Abu Dawud)
(Hadith taken from Muntakhab Ahadith in Solah Sunnah and Nafilah by Maulana Muhammad Yusuf)