You'll get every type of response on this topic from "real bassist don't use picks" to "I use a .38mm (REALLY thin) cause I can play faster". My advice is to determine two things; 1- the thickness you like and 2- the shape you like. It's all subjective really. There are many thicknesses to pick from but most bass pick players tend to use anything from .88 mm on up to 3 mm with most falling around 1mm. There are three basic shapes that are most popular, the triangle (also called a 348), the "standard shape" (pointed triangle or 351) and a smaller teardrop shape (called a jazz or 358). There are other shapes but these are the most prevalent. What you need to do is go down to your local music store, or order online, and buy a few picks in various shapes and thicknesses. By trial and error, you will be able to decide what is best for YOU! Don't play a brand/thickness just because your favorite bassist use one, use what's right for you. Now, what I use is a standard Clayton Acetal 1mm. I like it cause it the style I used when playing guitar and the Clayton's seem to be a bit bigger than everyone elses standards. I have used Dunlop nylons in 1mm and the Tortexs in 1 and 1.14 mm and they are good picks. But trying to find the perfect pick is kinda hopeless, like finding the perfect strings, but just have fun and enjoy the hunt!