What can I do to prep my skin for a TCA peel?

TCA peels must be performed by practitioners familiar with all aspects of the treatment (pre, post,complications). I highly recommend that you not attempt to perform this treatment on yourself. 20% TCA has inherent risks even with skin types I and II. There are several pre-op medications to take and that is one of the reasons you should rely on a professional for this treatment. 

all of my patients prep with enlighten or cosmelan and we have the post care for it as well on our cosmetics site. see link here but please ensure you are doing this and the right skin care prior to an inflammatory peel that has risk of hyperpigmentation. Best, Dr. Emer.

There is nothing you can do to prep for a home TCA peel. TCA is unpredictable and something that only a very experienced applicator should use. I have seen very severe problems after a TCA peel by very experienced physicians. This is why Obagi developed the Blue Peel by mixing TCA with a dye to give a more definitive end point and make it safer. Though much safer than plain TCA, it still requires an expert, not someone doing it for the first time. Toss the TCA and, when possible, see a professional. They will let you know how to prep.