When I had my Tahoe, I used a mix I found on another forum (Cadillac). They suggested dissolving a bar of Dove soap in around 1/2 cup of water (may need more to get a paste-like consistency). When I did it, I ended up shaving the soap into the water with a knife, since putting the whole bar in never even started to dissolve it. As the soap softens in the water, stir it around until it all gets soft and becomes a "paste". Once it is in a "paste", use a soft rag and rub it into the leather to clean and condition.
It worked very well for me. The Tahoe was about 6 years old when I got it, and the leather was a little soiled in some areas. Scrubbed it good with the Dove soap paste, and they were clean and supple as new. I repeated it a few times while I had it, and it always worked great.