Tawassul is of three types:
1) Permissible Tawassul; seeking nearness to Allah through means that have basis in the Shari’ah. Such as, for one to directly address Allah saying: O Allah, I ask You by Your Names and Attributes; my good deeds; or the supplication of such and such righteous person.
2) Bida’i Tawassul; seeking nearness to Allah through means that have no basis in the Shari’ah. Such as, for one to directly address Allah saying: O Allah, I ask you by the right of your Prophet, or an angel, or a saint etc. This type of tawassul is a point of contention amongst the scholars, and the difference is a legitimate one, which does not require censure.
3) Shirki Tawassul: seeking nearness to Allah through means that have no basis in the Shari’a, while addressing other than Allah. Such as saying: O Prophet, forgive me. O ‘Abd al-Qadir al-Jaylani help me, etc.