Bhagavad Gita · Karma Sannyasa YogaChapter 5, Shloka 27 (5.27)

Three steps:

1. Objects outside. Shankaracharya: śrotrādi-dvāreṇa antaḥ buddhau praveśitāḥ śabdādayaḥ viṣayāḥ tān acintayataḥ śabdādayo bāhyā bahir eva kṛtāḥ bhavanti — by not dwelling on the objects that have entered the intellect by way of the ears and so on, they are put outside. That is, "putting outside" = giving up dwelling on them, not shutting the ears.
2. Gaze between the eyebrows. Ramanuja: cakṣuḥ bhruvoḥ antare nāsāgre vinyasya — fixing the eyes between the eyebrows, on the tip of the nose (in keeping with 6.13 sampreksya nāsikāgraṃ svam).
3. Even breath. Ramanuja: ucchvāsa-niḥśvāsau sama-gatī kṛtvā — making the in-breath and out-breath move evenly. And the preparation beforehand: yoga-yogyāsane ṛju-kāya upaviśya — sitting upright on a seat suitable for yoga.

The difference: Here both acharyas are nearly the same; the difference lies in the meaning of "muni" and "mukta" in 5.28.