If you are speaking about the sink basket, the most important thing other than tightening it properly is Plumber’s Putty. However, if you are speaking about the pipes under the sink. The most important part, other than properly connecting them, is the washers.
I have a stainless steel sink(unknown manufacture) and the cauking around the drain is leaking. It seems to start leaking again after about 3 or 4 months. I used Plumber’s Puddy and it does not seem to help!