These days my main steels are CPM S30V stainless, CPM 3V tool steel and O1 tool steel. I heat treat the O1 myself and send the CPM stuff out to Bos Heat Treating, and they do great work.Thickness: I make knives from 1/8", 3/16", and 1/4" stock. With proper grind and edge geometry they can all be made to cut very well, but it is important to realize that generally, the thicker the blade the less slicing ability it has, while being a stronger blade. It is best to envision what you will be using the knife for the most and choose accordingly. 

I prefer 3/16" knives for the most part, as they give a good balance of mass and slicing ability. Most of my knives come with a full flat or convex grind, so they all slice well, but for harder use applications I tend to make the cross sections a little thicker. 

I currently am making my knives from a variety of steels. I will try to describe the attributes of each and the pro's and con's of each one. 

CPM154- A premium stainless steel that makes awesome hard use knives. Takes and holds an very good edge, a little harder to sharpen than high carbon steels, but great for guys who want the advantages of stainless blades. All my stainless knives are heat treated by Paul Bos. I use a matte or a hand sanded finish. 

01-is a common machine tool steel that makes a very high quality blade. Of the carbon steels I use, it offers the best edge retention and very good toughness. It is more expensive than 1084 or 5160, but well worth it. 

1084- a high carbon steel that makes an excellent knife. It takes and holds an excellent edge, and is easy for the average person to re-sharpen. When differentially heat treated, it has a very nice hardening line. 

5160-a great high carbon spring steel that is used for large knives that will be choppers and subjected to shock. It holds a good edge, re-sharpens easily and can be parkerized or polished. I like to use this for knives over 7", and with a differential heat treat. This steel has stood the test of time and will not disappoint. 

High Carbon steels will rust if it is neglected, therefore I would only recommend this steel for the knife guys or to those who are committed to performing maintenance. You are a knife guy if you have your knife in your hand at least 10 times a day. Guys who use their knives this much don't tend to get them rusty. Maintenance is as simple as keeping the knife dry and cleaning and oiling it once in a while. A coat of carnuba wax or renaissance wax is great for all knives too. 

For a knife that you plan to leave sitting in the sheath for who knows how long before you might need it, one of the stainless steels would be better. 

High carbon steels can also be parkerized. Parkerizing is a process that leaves a heavy black oxide on the surface of the blade. Parkerizing is porous, and is a great surface to hold oil to prevent the blade from rusting, plus it looks very good in my opinion. Parkerizing is a 100 year old process that is still used today on military weapons. 

I like park better than coatings because it is part of the steel. Even when it begins to show wear, it still protects and holds oil. it is easy to re-parkerize; that is not the case with coatings.