Starting and ending du`a with blessings upon the Prophet
Question

 
Before supplication, I praise Allah, ask Him for forgiveness and then send 'Salaam' on the Prophet (may Allah's peace and blessings be upon him).
After the supplication, I again send 'Salaam' on the Prophet (may Allah's peace and blessings be upon him) and then praise Allah.
Am I doing right, or is there some 'bida' involved in this?
Praise be to Allah.It is mustahabb for the worshipper to begin his du`a with praise of Allah, then to send blessings upon the Prophet (peace and blessings of Allah be upon him), then to ask for whatever he wishes, because of the hadeeth narrated by Abu Dawood (1481) and al-Tirmidhi (3477) from Faddaalah ibn ‘Ubayd (may Allah be pleased with him) who said: “The Messenger of Allah (peace and blessings of Allah be upon him) heard a man making du`a in his prayer without glorifying Allah or sending blessings upon the Prophet (peace and blessings of Allah be upon him). The Messenger of Allah (peace and blessings of Allah be upon him) said, ‘This man is in a hurry.’ He called him and said to him or to someone else, ‘When anyone of you makes du`a, let him start by glorifying his Lord and praising Him, then let him send blessings upon the Prophet (peace and blessings of Allah be upon him), then let him pray for whatever he wants.’” (This hadeeth was classed as saheeh by al-Albaani in Saheeh Abi Dawood, 1314). 
Al-Bayhaqi narrated in Shu’ab al-Eemaan that ‘Ali (may Allah be pleased with him) said: “Every du`a is not responded to until one sends blessings upon the Prophet (peace and blessings of Allah be upon him).” This was narrated by Baqiy ibn Mukhallid from ‘Ali in a marfoo’ report, i.e., it was attributed to the Prophet (peace and blessings of Allah be upon him). (This hadeeth was classed as saheeh by al-Albaani in Saheeh al-Jaami’, no. 4523) 
‘Umar (may Allah be pleased with him) said: “du`a is detained between the heavens and the earth and no part of it is taken up until you send blessings upon your Prophet (peace and blessings of Allah be upon him).” (Narrated by al-Tirmidhi, 486; classed as hasan by al-Albaani in Saheeh al-Tirmidhi, 403). 
Imaam al-Nawawi (may Allah have mercy on him) said in al-Adhkaar, p 176: “The scholars are agreed that it is mustahabb to start one’s du`a by praising Allah, then sending blessings upon the Messenger of Allah (peace and blessings of Allah be upon him), and to end the du`a in the same manner. There are many marfoo’ reports on this subject (i.e., reports which are attributed to the Prophet (peace and blessings of Allah be upon him)).” 
Note that sending blessings on the Prophet (peace and blessings of Allah be upon him) take three forms:
 1 – Sending blessings upon him before making du`a, and after praising Allah, because the Prophet (peace and blessings of Allah be upon him) said: “When anyone of you makes du`a, let him start by glorifying his Lord and praising Him, then let him send blessings upon the Prophet (peace and blessings of Allah be upon him), then let him pray for whatever he wants.” (Narrated by al-Tirmidhi, 3477; classed as saheeh by al-Albaani in Saheeh Abi Dawood, 1314)
 2 – Sending blessings upon him at the beginning of the du`a, in the middle and at the end.
 3 – Sending blessings upon him at the beginning and at the end, and one’s personal request may be made in between.
 (Adapted from the words of Ibn al-Qayyim in Jila’ al-Afhaam, p. 531).
 Based on the above, what you are doing is valid and is in accordance with the Sunnah.
 And Allah knows best.