The first major factor is the overall size of the knife. My preference is for smaller knives. You can get some really monster-sized folding knives, but are you really interested in carrying some that big? Face it, pulling out a large knife might impress your friends with your machismo, but if the darn thing is sitting at home because it is not comfortable to carry, it is doing you no good. official site
Most of the uses in day-to-day use for a pocket knife are quite modest. Most often I cut string, tape, cutting into cardboard boxes and other product package material. You most often are not hacking up tree limbs or anything, and if you are, get a tool designed for that! I would recommend a blade of four inches or less. One of my favorite knives has a blade of two inches.
Another factor to consider is the blade configuration. In other words, some knives have a single blade, and some have two or more. Many knives have two blades, usually one larger, and one smaller blade. I have owned them in the past. For the most part, I found that I used one blade almost all the time, and the second blade almost never came out. I suppose there might be time when having the second blade is useful, but again for almost all daily uses, a single, sharp blade is fine. You do not have to spend a lot of money to have a quality pocket knife that will last you a very long time of dependable service.